Modding: Doctrins

[dmm]

You could do this if they were in a single line of research. For instance: Wealth, Jihad, Innovation. Then, Wealth gives +10% mining, Jihad gives -10% mining and +10% construction, Innovation gives -10% construction and +10% research. So each doctrine cancels the prior benefit and substitutes its own benefit. (Not sure how you would justify the order.) Perhaps the first one could be very expensive to research, and all subsequent ones could be very cheap. So then you could stop on the doctrine you actually wanted. You could even have levels. The levels of doctrines would be widely separated (in research points) but the choice of doctrines would be closely separated.
Example:
Wealth I....10000
Jihad I.......10100
Innov. I......10200
Wealth II....20000
Jihad II......20100
Innov. II.....20200
Unfortunately, you couldn't stay at Wealth I while researching Wealth II. You'd have to go to Innov. I doctrine for a while. You could justify this with some bad history/economics baloney.