Another idea that should make every game feel more different, giving variety to the game.
I proposed that certain Champion know a tech/spell that will allow you to use it as if you've researched it already.
For example, if at turn 1 you luckily recruited a champion that knows Advanced Trading, your empire enjoy all the
benefit of this tech immediately.
And when this champion dies, the tech goes away with him (unless you research it already). To make this kind
tech/spell carrying champion, I also like that whenever there is new spell/tech researched, there is certain % chance
that this new spell/tech will be automatically assigned to a champion that you owned. When this champion is married
off to other player, the tech goes to that player too (but your empire still have it since you researched it).
The point being, tech/spell should not be completely coming from research trees or goodie house. Associating them
with a champion will make gaining/lossing tech more dynamic and fun. Also, it should act as a reasonable way that
more advanced tech avaliable quite earlier under the right circumstances.
As an compliment to this suggestion, I would further suggest that when a champion loss a battle (i.e. his party being
slaughtered), the champion do not necessary die. They can sometimes stealthy escape to the nearby allied city,
recruited by the wining party, turn independant. I feel bad to see all that effort invested in developing a champion
is gone because of just losing one battle. Of course, it can be fun for a tech/spell carrying champion change alliance
to other party, allowing the winning player tech/spell.