Well, you could have cammo non the less, just basic cammo (like mostly gray, so that it could look like a scout, lets say, but when you look a little closer, you see a turret or something. That way, it moves fast, gets the same job done, but the enemy might just pass it off as an annoying freak trying to scout spam. Thou i still don't see why stealth seriously the most important part of war besides the battles them self) can't be included. for a colony might not want to go to war with another, but still stop them from making tanks, and send some stealth bomber to destroy factories (just like making all star flare units move same speed invisible as visible).
btw, do earth workers not get heart if the tube to a colony is cut first as hooman said?