Yes exactly: depending on region type they could even increase morale and loyalty and maybe even max tax rate, but too much will always be a net negative.
Maybe base it in number of men rather than CS, do you pick cheap militia to maximize tax rate and gold, or pay the extra to actually defend?
Most of all, I'd say milita in a city will always decrease stats, while a stronghold sees no negatives.
Oh: count militia against region population? Would stop piling militia in rurals.
