It would be nice if the game could have an alternative vision mode which displayed the units as wireframes. Also units seen in this way could have symbols meaning they are locked down, parasited, blinded, etc. To tell which units belong to which player, they should be surrounded with a team color aura, like WC3 heroes. This could be done just by pressing a key, like F8.
There is supposed to be an unofficial hack surfing the net called something like "direct x wireframe hack". Google didn't spit out anything useful though. I know it exists because I've seen a video of it a long time ago, youtube it here to see it in action. I'm no programmer but I assume the hack changes vital things in direct x files, making all direct x games wireframed. It's quite possible that I'm wrong though
The use is making the player able to see in an easy way which are the damaged units (just like pressing alt in WC3) and which are currently affected by spells.
They've already announced that they're incorporating the ALT feature....I suppose the spell bit would be nice, but I would rather they put in little Icons next to the health. And Blizz makes good icons.