I'd like to be able to have a viewport which only has geometry in it, and have another viewport which is only helpers, lights and shapes, and then maybe a 3rd viewport which is geo + lights. Currently there is no way to do this.
This would make lighting a lot nicer utilising Nitrous, it would make animating better as you could have bones visible in one viewport but not the other. It would make rigging better as your rig could be hidden from your camera view.... etc.... etc...
If you like this please post your use-case scenario for this. I firmly believe this one feature will benefit 80%+ of users on a daily basis and thus should be way above the priority of anything like Biifrost for max etc....