I'm in the camp that believes that leader/civ abilities should be significant enough that you plan your game around them. I feel like this increases replayability if abilities to leaders/civs aren't simply small boosts, but significant boosts ideally tied with mild/moderate nerfs
Pachacuti was a good example in civ 6. His ability to work mountain tiles meant you interacted with the map in a fundamentally different way than you would with other leaders, and so long as you had enough mountains around you, playing him felt like a kinda unique experience compared to other leaders. I also like the idea of hammurabi in civ 6 but he's just too strong IMO, but his very unique ability is per se a good thing
interacting with the map is just one way for this to play out, though. With all the added mechanics to civ 7, there are a lot of possibilities. Just some ideas for leader abilities that would make a game with them feel very different...
- get additional memento slots (also, I think it would be interesting if you could by default get 3 mementos instead of 2 if you used the 3 mementos tied to your leader, but thats a different topic)
- additional triumph slots moving into the next age
- idk exactly how to word this one, but something that de-nerfs city state suz bonuses. It used to be, for instance "+5 percent to wonder production for every city state you are suz of" now its +5 for every cultural city state you are suz of. Maybe a leader could have their suz bonuses be based on total CS suzeranity rather than the current benefit that is limited to CS suz of that particular type. Tell me that wouldn't make Greece or Siam more interesting
-automatically unlock the mastery to a civ/tech when you complete the parent civ/tech. This one would be pretty strong so maybe paired with a reduction in which ever of the two that you aren't getting the boost to, so minus X amount of science overall if youre getting the civic masteries when completing the parent civic
- Abe Lincoln was apparently pretty tall in a day and age when ppl didnt grow that tall, so maybe a buff to settlement growth but a significant reduction to settlement cap and a big penalty for going over (or maybe straight up cant go over)