Well I am currently after a similar goal for use at work. However, I am also trying to keep the flashlight somewhat small, lightweight, and safe. I've decided upon a 3C Maglite running 3 NiMh C cells through a 3mode 1.4A AMC7135 driver powering an XP-G R5 neutral white. The NiMh C cells are rated at 5,000 mAh (no idea of "true" capacity). If weight and size were not an issue I'd do a 3D NiMh Maglite with 10,000 mAh capacity! These batteries are of course in series to get 3.6v. The driver is 3 mode so the light can be used in medium to conserve battery much of the time. (Although I might be interested in bumping medium up higher than the current 30% level.)
I chose the XP-G so as not to "waste" battery power on the spill and get a little bit more throw (in my case throw was needed and not much flood). After seeing how an XR-E Q5 can perform nicely without having an annoying narrow pencil beam, I might even consider it.
-Garry