Pathfinding for units in Red Alert 3 was awful, and the next C&C title must improve on it.
Fundamentally, something that takes great satisfaction away from playing Red Alert 3 is the awful pathfinding. There's simply no way around that assessment; large units sometimes decide to stop and not do what you told them to, while groups of large vehicle spread out to the point where micromanaging them is difficult and needlessly effort-intensive.
I think it'd be much better, as in sc2, if units moved to a point in their present formation, and then if the player clicks for them to go somewhere close they will automatically try and bunch up, like ants attacking something. In Red Alert 3 it is so frustrating that units have a mind of their own and always choose the daftest formations and spacing.
Units do what the player wants them to do.
Less lunch breaks for aircraft carriers.