It would be nice if we could give the computer players a bonus but be flexible in what areas the bonus applies. As we know, Low bonus gives x2 to intel, research, and resources; medium bonus is x3 and high is x5; and construction rate is x1.5, x2, and x3.
Sometimes I want to play against A.I.'s that have lots of bonus ship production but not necessarily more intel or research. So I think that can be done by using cultures. Instead of using the standard Low, Medium or High bonus to the computers, assign a new culture to them that includes the bonus.
So, for example if an A.I. has "Warrior" culture, it normally has -2% Research, -2% Intel, +5% space combat, +5% ground combat. If you want to give it a high bonus, instead of using the high bonus in the game settings, you could assign a new culture "Warrior with high A.I. bonus" that has the equivalent bonus: +400% production, +398% research, +398% intel, +5% space combat, +5% ground combat, and +200% space yard rate.
Then, if you wanted to give the A.I. a bonus to resource production and construction rate only, you can create additional cultures which have bonuses in those areas only and assign them to the A.I.s.