My idea is as follows: You have four tiles left for building on a class 8 planet, and they are positioned in a form of a square.
If you build factory on one, and another one on the one next to it, the factories would link, and work together to make higher industrial outputs. Do so with two left tiles and what you have is a mega-factory.
My suggestion - Building same improvements on tiles next to the first one (the factory) would improve their overall efficiency.
Two factories: +2 ind. points each
Three: 1st 2 unchanged, +1 for third
Four: 1st 3 unchanged, +1 for fourth
Ten: Mega Manufactoria: +1 more for all
More then Twelwe: Forge World Bonus: +1 more for all
The bonuses can not be influenced by other bonuses, such as power plants or Capitals, but a research to do so would perhaps be also possible?
Such a thing would, of course be perhaps doable with the research labs as well.
It's for TA, of course
EDIT: I seem to have ignored the flashing word "IDEAS" and posted it here. AAAAAA D:
EDIT: And maybe for Generators to only give onuses to factories connected with them?