As for now all units' wreaks have 90% mass and hp of the original unit. In t1 stage almost all wreaks get overkilled by arty fire. But t3/t4 wreakages keep their mass most of the time. Which encourages not to attack unless you're shure to win and beeing able to reclaim the whole battlefield.
My thoughts would be give all units 0.45 (includes buildings too) mass multi and increase the health multi maybe to 2 or even more. On t1 mass will be quite the same but on t4 stage attacks will be way better than turtling.