Which units would you replace in the Sylvan castle?

I'm not upset with you, but I just think that some factions, like elves (and especially the undead), clearly lack units. We could simply add some. All the current features of the version will remain for those who are already satisfied (and the units here are really well-chosen, but some are clearly missing, like death knights and pegasi, and there's nothing to replace them with), while those who feel that there aren't enough units will get new options.