Part of the problem with Agricultural is that sort of acts like a not-so-mini version of Productive and Imperialistic in that it accelerates your first few workers and settlers about the same as those traits do because you're generally building them out of food in the early game. If Agricultural provides an extra, say, 120 food over the first 50 turns, that's an extra settler or 2 workers without even considering extra production due to faster growth time, etc.
I like your "Coast provides irrigation" and "Food costs for new citizens increase half as quickly" ideas. The first one gives you something cool and definitive along the lines of creative's easy early border pops, allowing you access to city sites that other civs would ignore early. A coastal rice with some nearby hills might be a desirable production site settled as one of one's first few cities rather than some forgotten filler settled in the AD years. Decreased bin costs is also pretty cool, because it effectively gives extra food without the side effect of mimicing productive's worker boost and imp's settler boost; its also definitive in that it would encourage growing ones cities more early. Would be extremely strong late-game too.
If that's not enough, Agricultural civs could also spread irrigation at, say, Pottery the way other civs do at Bureaucracy. At any rate, I think its cool to have more tactical options and flexibility rather than straight numbers increases.
I like your "Coast provides irrigation" and "Food costs for new citizens increase half as quickly" ideas. The first one gives you something cool and definitive along the lines of creative's easy early border pops, allowing you access to city sites that other civs would ignore early. A coastal rice with some nearby hills might be a desirable production site settled as one of one's first few cities rather than some forgotten filler settled in the AD years. Decreased bin costs is also pretty cool, because it effectively gives extra food without the side effect of mimicing productive's worker boost and imp's settler boost; its also definitive in that it would encourage growing ones cities more early. Would be extremely strong late-game too.
If that's not enough, Agricultural civs could also spread irrigation at, say, Pottery the way other civs do at Bureaucracy. At any rate, I think its cool to have more tactical options and flexibility rather than straight numbers increases.