It's disappointing, that most of the feedback here are small balance changes, instead of really thinking what you could change.

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IMO changes could be:

1. Idea groups at different techs (e.g. 3, 5 ,7, 10 ,12, 14,18, 22, 26)
2. And yes The number of idea groups could change too.
3. You could make idea groups weaker and reduce idea cost
4. Or less ideas per group
5. The Requirements could change -->You still have the same adm tech lvls for idea groups as before, but e.g. on dip 10 and 20 you get a diplo idea group which costs less (Same for mil).
6. I'd like idea groups for specific governments reforms (Won't happen though, cause it's a dlc feature)
7. You could let idea groups build on each other. E.g. If you want to take exploration you have to take maritime first

Any other ideas?