I haven't read all the ideas, so maybe these have already been suggested:
1. Once the garden is irrigated by building the dam and diverting the stream, watering the garden seems unnecessary. Maybe the farmers could find some goats and breed them for milk and cheese. The builders could build a stable or barn with fences or something to gain skill too. Additionally, the garden could be increased in size as the population grows.
Farmers could also develop the tools and ability to fish with a pole and line from a wharf built by the builders.
2. Tropical fruit trees could be earned or added for something else to harvest.
3. Either have the sick villagers go to the hospital when they are sick and have the adept and master healers hang around there, doing research when they are not busy, or do away with the hospital and let the sick villagers continue to go to the village center for healing.
4. Let the builders build a school when the population reaches a certain milestone and have the adept parents do the teaching for skill points. I like the school in VV1 because I could always bong the drum to get all the children in one place and check on their conditions, etc. rather than have to scroll through all the profiles in the details area.
5. Create a list of villagers with general information (age, health status, skill levels, ???) as the opening screen for the detail area, then allow the villager to be picked for more information. It would allow a quick search for information rather than having to go through all the villagers looking for those who are sick, weakened, elderly, etc. This would be particularly helpful when the player is near the population cap.
6. Expand the size of the research table when higher levels are reached, it is hard to find villagers when you have 15 or 20 researchers at the table.
7. I agree that nursing mothers should be contributing in some way. Teaching, telling stories, things that will not get in the way of caring for the child, it seems silly that the mothers just sit in the village center and do nothing.

That's all I can think of, hope some of these help.