Currently when playing a game with handicap enabled, increments of only 5% are possible.
I am suggesting that smaller gaps between intervals i.e., 1% should be a thing.
I would also like to see decaying Handicap and negative Handicap.
Many players struggle with the Early game and get overwhelmed by Hard AI but Medium AI is too weak in Imperial Age. So an easy solution would be to give them a Handicap that reduced over time. My idea would be to make it go towards 0 by 1% per Minute. So a Handicap for 20% would be at 0 after 20 Minutes. Still helping with the early game but then not making the late game too easy.
You could then also do the reverse. Give the Extreme AI a negative Handicap that slowly goes to 0%. So you can get a head start but then have a challenging late game.