It would be very cool, yes. At the mean time, what you can do, is to use morph commands. Morph the unit into a separate unit of the same name with an underscore at the end (it won't appear in game) so they appear to be the same unit, but because they are actually a different unit, you can give them different models and animations. For example, you could morph a unit into one with a different weapon, or pull a transformers move and turn a car into a giant robot. Abet, what they lack is the ability to make *all* units like that, as an upgrade would, so yeah, having different animations with upgrades would be pretty cool.