Urban Sniping, How to Carry it All

I have need of some advise from you all. I am going to be playing as a sniper in a few large events this year. They are all 2 day events with a couple being 24 hour events.

I need to a way of getting to my M14 easily (or at least have my Spotter get to it easily) while not restricting my movement. I'll be carrying an XCR and M9 also as the M14 won't be out unless I'm set up in a good position.

If anyone has suggestions for a pack mount or something similar I would really appreciate it.