That E20 could work but it appears to be a single mode light.
Picturing your use for this light, if it were me, I'd want the following features:
*Comfortable to hold for extended periods.
*The AA nimh seems like a good choice because you'll go through a lot of batteries with daily, extended use and I don't believe there is any cheaper way to go.
*Multi level with LOW first. Think about it . . . checking IDs will be the number one use and you don't want high for that. But you do want high for challenging the impatient rowdy guys 10 feet back in the line.
*Belt clip. The line won't be there all night (and a lanyard will make the rowdy guys laugh at you) and I'm sure you have indoor duties as well. You need a place for quick access. A belt clip makes sense.
The Surefire L1/A2 etc. type UI would be optimal for this (except that puts you back in CR123 land). You get low first or immediate high if you just mash it. Keep in mind that unintentional mode switching or cycling through modes would be very annonying in this scenario and might give a bad name to flashaholics everywhere!!
Another UI that would work would be the EagleTac with the twist head. You can use it on low all of the time, then twist for high when you need it. It's a forward click so you can have it momentary, or click for locking it on. The only downside is two hands for switching to high.
A bouncer is one of those applications where a strobe feature might someday be useful (maybe, I don't know, I'm just thinking about all of the different scenarios) but it will be tough to find one light to do
everything I suggested above, AND have a strobe too.
Let us know what you decide.