"Deployments" indicates a somewhat different environment from my relatively tranquil civilian situation. You might consider 14500 (size equivalent to AAs). I believe there are lights like the Fenix LD09 that will accept either battery. I am a definite fan of rechargeable batteries - essentially they are much cheaper in the long run and the li-on versions offer much more energy density, although the do require attention and some understanding.

I retain dedicated AA lights, as well, because of the almost virtual availability of AAs, but all mine utilize rechargeables - primarily because of lower cost.