You could prob loose 'some' weight by using 2wd and a belt between drives. saves weight on motor gearbox (but gains on belt and pulleys?

also you wouldn't need those large plates to hold the motors in place, something like these will do: (shameless plug - i do sell some)
also the plastic casing around the linac could be striped back a bit. i have a couple of those actuators and although i haven't striped mine, they do look as if they can be.