Kestrel
Flashaholic
Although the SF P-series are quite flexible as the OP has noted, I'd very much recommend the two-mode SureFire L1. Somewhat slimmer and rock-simple UI for the two modes.
This sounds like a great option. I've of course seen the Nailbender name tossed around as well, but where would I go to look at the drop in options?
In thinking about it, changing batteries mid-race is really not an option. Perhaps I should be looking at something I can put an 18650 in?