Can it? And how stable or CPU hungry it is? I would like to add the extra layers but if the mod is still somehow experimental, I sure don't want to lose my current game.

not that bad, just had some optimizations added.
make saves. i haven't had corrupt save

The game is fully stable. I have a medium base (about 600 science pack/min) with 137h of play time. No problem. With the last optimizations, the script update time is around 1 ms per update (for all mods, full modmash stack)
Playing with multilevel is really funny.