I’m a rigging noob probably, but when something starts to lag very hard, I think it’s a bad idea immediately and think of something else instead. I just finished a movie, and every single rig is blazing fast. Though on the other hand I know that those rigs could be better in terms of actually helping me animate.
Maybe you need to do a proxy system. Make a rig / model that is there for animators that runs fast. And then make an additional, hidden rig on top of that is only available when you are rendering ( or when you need it ) that will do all of the minor detail work.