putting raks in garrisons is pointless
Well it is not a very good option but I would not go so far as to call it pointless.
The benefit of moving RW into an ambient building is that now fire from a higher elevation and from what I have seen it has less chance to collide with ground so it can get more collision hits.
Most of the down side from using garrison comes from flaws to RW veterancy bonuses that are geared toward camo and thus garrison RW do not benefit from it. Veterancy bonus of the RW is actually something that should be looked at along with camo mechanism that is not player friendly.