Well, +2/+1 adamantium would still be very powerful, not just as gamebreaking. I'm not so overly concerned by it though.
For me tweaking the production would achieve the same.
Your mountain nerf could have already achieved balance, I'd need to see that in practice before commenting. Is it in 5.02?
For food, I've always considered the low desirability of coastal towns really weird. If you can't make oceans suddenly productive how about raising the food of coasts and reducing a bit grasslands to compensate? Both 1 would be a good ratio for me. (Remember that there's rivers on land that already raise it so it's not such a big nerf for grasslands)
For me tweaking the production would achieve the same.
Your mountain nerf could have already achieved balance, I'd need to see that in practice before commenting. Is it in 5.02?
For food, I've always considered the low desirability of coastal towns really weird. If you can't make oceans suddenly productive how about raising the food of coasts and reducing a bit grasslands to compensate? Both 1 would be a good ratio for me. (Remember that there's rivers on land that already raise it so it's not such a big nerf for grasslands)