i don't think trying to go "low-powered" is a very good idea. mountainous itself is really bad for town in-practice (regardless of the calculated EV), but more relevant is the fact that town gets a
lot
more out of power roles than scum do – it's sort of a natural element of skew in favor of town that exists in normal games. even the best scum roles really can either only block town roles or gain information about them and these aren't really that high-value for scum, but the best town roles can reveal people's alignments and even kill scum, which are super high value.
we definitely should be adding a high-power role to the setup even if scum get balanced to be more powerful because of it – town benefits a lot more from power roles than scum do anyways.