Regarding the Builders:

They need more to do!! Once you have built the huts, dams etc, there is no point in training up more builders. I think that it would be cool to see storms that show actual damage to huts (Sort of like how debris washed up on the shore in VV1), or that huts fall into disrepair after a certain amount of time.

Farmers:

What about having cattle pens, sheep, pigs etc? Maybe you could have farmers that cultivate flower gardens etc.

Doctors:

They could grow medicinal herbs too

Cooler secrets:

I think that it would be exciting to have the villagers stumble upon some sort of passage way that is blocked. You could have the villagers remove the blockage and stumble upon and open up a whole new area! All new huts, stores, temples etc. to be rebuilt! THe sky is the limit!!