I think the kingdom rush series can learn a thing or two from Iron Marines. The most obvious IM mechanic that can be used in kingdom rush as well, is the ability to move units by swiping to the destination you want your units to go to. That would make micromaninging barracks much more fluid than the current rally point system. Another benifit is that this allows you to put your units at their maximum rally range more easily by swiping over the border of the rally range.
Another thing that can be carried over from IM is the ability to target a specific enemy. Obviously this should only work for heroes and barracks, not for any other towers. Now, it can be really annoying to get your hero to fight a specific foe in a group of enemies. A simple targeting system could solve this.
Are there any other little improvements you can think of that could improve the upcoming kingdom rush game?