Just a quick suggestion that I think would be really helpful. A button that you can press or hold down that causes all selected units to ignore the other units in their group and head at top speed towards the destination. You can do this with A (attack-move) if you're trying to get to an engagement, but if you're trying to run away this just makes them stand and fight. In emergency retreat situations, this would really help preserve as many units as possible.
??? Well, in other RTS it is the other way around. Move at individual top speed is the default and move at speed of slowest unit is the special mode. But it's still the same thing. Just two examples: So, in supcom all units move at top speed by default. Only through your dedicated command they move in a formation at a common speed. In WC3 you have a toggle for the two modes.
I like that PA defaults to same-speed, as it never seemed practical to use in SupCom for some reason. But being able to double click (perhaps not as some people spam-click out of habit), or just press the speed modifier button before you click would be wonderful for unit control.
I prefer it this way too. On top of that in supcom it's kind of buggy as the pathfinding in its entirety.
I'd like to see an RTS bring back the old C&C scatter command, which basically forced your troops to run a few steps away from everyone else. Good for avoiding carpetbombing/artillary.