Based on title im not talking about the assembly project. First there needs to be two, not one big tech trees. Synthetics needs to have their own. Synthetic needs to have at least some of the colinising events that are their own. I am talking specifically about growth and food. 

The yor should get free social production 20% to make up for having to build instead of free population. 

As far as the power plant techs they either need another power plant to make up for their population penalty, like the thalan, or the power plant need to either be a research, or manufacturing building, or both that, and a population building.

Because lack of farming techs, and buildings to speed this up if you havent already done this they would need more manufacturing techs to balance this.

We could do something like two with a few changes with the charging stalks we would remove the growth because of the assembly. We could still increase population limits without any growth, because tbe assembly does this.  would add an intimidation branch instead of not having a diplomacy branch on the tree. We could get rid of economics, and governments if we replace these techs with raw production techs. The production would balance not having economics. We would have to add more wonders to balance lack of wonders. With these changes twos tech trees would be better if we add a power plant branch to it.

I would give you that social manufacturing seems more powerful untill you remember that you still need to build population. Its just more flexible. You could fix this by minusing it at the end of the branch, and remember the yor  originally had a bonus. You might think production is better untill you remember that money affects production the same way with allocation with a lot of pther benefits. I could allocate spending with for production, or i could buy something with it can raw production do this no. I can influence other people with money can raw production do this no. I can rush buy with money can raw production do this no. Money is more flexible than raw production not weaker.

To balance this i would make these techs untradeable where the yor cant get economic, government, and diplomacy techs. And organics cant get production or intimidation techs.