I'm not finding anything about this in the modding PDFs, but I'm sure it's common knowledge that somehow is escaping me.
Q: How do AI nations and Indies establish their research level? Can you set it via modding, or perhaps their research speed?
I ask, because in one of my mods I have playtested SP many times, and high-level Indy mages never seem to cast high-level spells even in late game. For example, a F7A2 mage, at turn 60+, still refuses to cast anything higher than "magma bolts" or whatever... and he's loaded with fire gems. My own research levels at that point were 6+ in about everything.