This is the same line of thinking that I've applied to my "at work" BoB. I can shed some gear if need be and I can still move freely while walking or running.

I still have to split some gear between bags (MRE's with water), and move some items (of lesser importance) into bags that would be shed first and easily (quickly) if the need arose.

I really like the use of your ammo pouches to carry water. They might also be good to carry a FAK, TP, and small incidentals.