Here's some thoughts on a few leaders I've tried. These were all single player games with restricted leaders; specifically, I played some of the leader/civ combos I consider to be some of the worst in the game for single player. Difficulty was Immortal/Pangaea or Non-Isolated Fractal, standard speed; I can beat SP Deity with better leaders, but wouldn't even bother trying with these guys unless I had a pretty phenomonal start.
1st and 2nd games: Tokugawa of Japan, Hikikomori 4 Lyfe.
Playing this guy feels you're starting a marathon with a rocket pack strapped to your back. Blazing expansion speed with the ability to put infrastructure at a matching pace, but always the potential to get your face smeared against the ground once you run out of fuel. (that is to say: you better get some cottages up pronto!)
Japan starts with The Wheel and Fishing, which is pretty decent combo now. Starting with the wheel (or being able to research it as the first or second tech) feels very important for productive civs as they're going to get out lots of workers very early and also start producing settlers very early and it can be easy to fall behind on infrastructure. I'll come back to this for Charley, because that's a weakness he has that Toki doesn't. Fishing/TW also lets you get pottery as your first tech, if you want it, or a cheaper pottery later if you need to get Agriculture first.
Tokugawa's traits have a bit of synergy in that together they act as kind of a pseudo-imperialistic trait. Consider that, at size 4, due to the workboat start, my capital could work a 7f farm, a 5f crab, a 5h mine, and a 3h forested plains hill, which gives 15h/turn into a settler. An ordinary civ would get 12h/turn, and an imperialistic civ would get 16. Tokugawa is almost as good here. A size 3 city w/ a non-seafood start (not working the forest-hill, and say a farmed banana instead of the crab) would get 14/11/13, respectively - Tokugawa would actually produce the settler faster than the civ with an explicit settler production bonus!
At any rate, Tokugawa really values tile efficiency above all else, but desperately needs commerce. Thus, I found that satellites are particularly good for him. I mean, I always like to do the ring-around-the-rosey capital thing but it feels particularly useful here even with other cities. For example, one such city of mine, in my second game, settled on a plains hill with no resources but a single copper mine in its first-ring of tiles. (gaining me my only source of metal in the ancient and classical ages in that game). This was a 1f/6h tile under productive, which yielded an incredible total of 13h/turn into a worker! For a size 1 city!
That little guy produced a worker every 4-5 turns for quite awhile. Later on it switched to working up some cottages for another, much-nicer city until I could chain some irrigation over there to turn it into a respectable entity in its own right.
Between being able to grow fast and being able to get a lot of production out of tributary cities really helps you work a lot more commerce tiles than you would otherwise be able to. However, because of that I also felt really cramped for happiness resources. Most multiplayer games aren't played on Immortal though IIRC, so that should be better than my experience here. Because of this though, I tried out Boudica next. I didn't find any stone in either game, so I didn't try out a midsrep+caste combo, but I think it would be very good for Toki.
Anyways, I liked him a lot. Obviously his traits would make him completely insane (by far the best leader) if the game lasts long enough for a civ to get chemistry+biology+communism, but generally games are decided by then anyways so its not worth worrying about too much I think.
3rd game: Boudica the Boudacious
I had a bit of an abornormal game here which might have colored my opinion of Boudica, both good and bad. My capital was pretty crummy; no river, coastal with no seafood, 2 grassland cows and a pair of spices, not much forest. Celtia's starting techs remain abysmal; even with the relatively better starting commerce bonus (since both hunting and mysticism's tech prices are increased), I'd really rather have a tile I can improve out of the gate. If I had a deer, fur, or ivory around, it woulda been OK though. As it was, though, I went AH->Mining->BW, and worked the cows and a pair of mines (one of which was a grassland gems!) for quite a long time. Without the gems, I woulda felt the pain of the starting techs a bit more.
That said, I actually quite like Hunting now; a 2-move scout now feels like a decadent luxury compared to the ordinary plodding pace, comparable to Creative's free city culture in some ways. (in that hunting leaders get extra information to plan your first few cities better, similar to how creative leaders can allow food resources to be a second-ring). I realize this was also the case before, but here it doesn't come at the price of "cheating" you out of your first warrior.
At any rate, I still stuck with my plan to see how well Boudica's traits translated into an economic bonus by amp-ramping-up a cottage capital though, settling my 2nd city partially into the jungle (but on a river) with a dry rice and bare wet sugar serving as another pair of 5f tiles to power the city's growth. The capital was able to work 3 cottages, and 2 other satellites worked another 3 apiece. I still got a palace up here pre-Bureaucracy with a city of size 13 (and quickly growing into all 16 cottages total thanks to HR and the big food surplus). Not bad, but coulda been better if the spots were reversed. Slavery + the extra food and happiness let me whip quite a bit of production out. It feels very important to whip as much as possible to get the most out of agricultural; I wonder how it would do with Alexander and Monty in that case.
I feel the extra happiness (and not needing the monument) is a nice bonus to Charismatic, but would probably be muted compared to here. Still, Agricultural helps you make the most of it... that is to say, if I saw a starting screenshot with lots of food, I'd definitely consider this trait combo, especially if I could get a better civ to go with it than the Celts.
4th game: The Burger King
My Charlemagne game started with a decent capital: moved onto a plains hill, had wet wheat and a plains cow, some river, lots of forests. No bare mines or river grassland though, again no hunting resources. Nothing suitable for early commence in a 10 tile ring around my capital. So, I stayed small started spamming out workers and settlers like no tomorrow, and expanded VERY quickly, having 3 cities and 3 workers by like turn 40 I think? I can't remember the exact number now, which is strange for me, but it was pretty ridiculous for normal speed. However, having lots of workers without neither bronze working nor the wheel was a bit of a problem. I grabbed TW as my third tech, after agri and AH, without time to get a road bonus to my second city's settler. BW came very late despite a good number of forests to chop and Pottery was delayed even later. I'd have rather skipped BW all together but I had no river-adjacent tiles without a forest or jungle nearby.
Not much else to say; I was able to expand pretty well and had lots of hammers to play with. Too many hammers, actually... I felt my civ started stalling pre-writing due to relative and inadvertent overexpansion and economic underdevelopment. To put it a better way, I felt like a mutant freak from some sort of sci-fi B movie, my muscles bulging out in real time to grotesque proportions as the secret serum started working its way through my veings, but yet, my mind mind remained that of a 4 year old autistic child.
Productive felt a lot worse here than with Tokugawa what with mining coming late and workers not having a full task-list available to them. My army of workers started pre-chopping forests just because they had nothing better to do, and building unworked mines, pre-roads, redundant roads, and roads to nowhere. A little bit of this would have been very good (can always have better defensive road networks, and always nice to have tiles improved before you need to work them), but it started feeling very inefficient. Throughout the game I always felt 2 techs behind where my civ's infrastructure otherwise should have indicated. Perhaps this is just a map thing; if you can see ahead of time that your start has a deer, maybe starting with hunting/mysticism wouldn't be so bad, but as it is, for an unseen start, I'd still rather have any other tech combo.
As for the other things: Rauhaus is still good but still overrated (unless paired with an unrestricted organized leader ofc). I actually did appreciate the half-priced market, but in the way I'd appreciate finding some still-wrapped hershey's kisses from christmas in my couch's cushions.
TLDR version- Tokugawa/Japan = pretty good
- Boudica/Celts = OK
- Charleyman/HRE = still sucks
Other changes- Didn't have ivory for any of my 4 ToW games - seems like a good change though.
- Workboat w/o fishing - great change, even though it didnt affect any of these games.
- Metalcasting - great change, I got this much earlier in general, especially since I didn't build the oracle once, compared to my BTS games.
- Wharf - seemed interesting but I didnt really have any coastal-heavy starts, so no comment.
- Fast worker seems overly harsh; you're effectively losing the first 4 turns of your worker every time you build one of these guys. I sure as hell wouldnt want India without a Productive leader, and then the two of them together might be overkill. Well, maybe I'd have to try it out first I guess.
Games were played w/o tech cost scaling, although the next one I try will be with that on. Leaders next on my list are Churchill and Alexander. Montezuma seems like he'd be really fun in this mod, with agricultural+sacrificial altars allowing you to go completely nuts with the whip, but I sure as hell don't want to do more than 1 more game with Mysticism/Hunting. Maybe I could try another civ that starts with Mysticism, like Justinian, Isabella, or The Wangster. (although, Financial seems pretty bad now... maybe an Oracle slingshot of Machinery could make it work, and is a more realistic possibility now that MC is so much cheaper? but then, HC would still be better...)
Anyways, hope this feedback is of some use. Let me know if you're interested in hearing any more feedback.