Yep, battery standardization is just a goal. Due to form & function limitations, it is probably not attainable unless you really fine tune your needs. If I only had one light the FourSevens QP2A has a wide range of output (0.3-336 lumen). Two AA batteries gives it good runtime on the lower power settings, but it has good throw if you go to the high end -- solid light imo. No affiliation other than as a past customer.

For quite awhile my go to light was the Gerber Infinity hikermor mentioned. I too have a couple, they're good lights.