Which units would you replace in the Sylvan castle?

In my opinion, everything is perfect here; I thought about it for a long time, but I don't want to change anything. However, if they added a second building for each level in some expansion pack, then for the fourth level, pegasi would be suitable for the Castle, for the seventh level - magical dragons, for the fifth level - magical white tigers from Heroes of Might and Magic IV, and for the third level, let's say, satyrs from the same game. It would be new and interesting.