True, Axalon, very true. I'd say 5-8%, and go ahead and scrap the rebuild structure idea. But they should leave a big half-destroyed building, and not just get blasted into a billion atoms just because it got hit a bunch of times with a laser.
I think the best way to implement this would be to allow negative hit points - when a unit hits 0% of its hitpoints, it breaks down and is unable to continue functioning. Units stop recognizing it as a target unless instructed. During that time it can be salvaged. If you tell them to keep attacking it, or if it was killed by something really big (supernova), then the more damage it takes, the less it can be salvaged for, or the less likely you are to be able to reverse engineer it. Advanced Labs would have docks, so that salvaged vehicles can be dumped in there instead, giving you a tiny chance to open up an otherwise unavailable research. Any cargo has a certain % chance to be salvageable, which again, lowers each time its hit. When it hits -100% hit points, it is blasted into tiny pieces that scatter all over and can't be salvaged.
IE: you have 2 laser lynx, the other guy has a supernova lynx and a microwave lynx. Your laser lynx have 300 hit points. The microwave lynx eventually whittles one of your lynxes down to -2 hitpoints. It breaks down and cant do anything. The supernova then goes off, and your other laser lynx takes 700 damage. Its now at -133% damage, and is blasted to bits.
What do you all think?