Ok here are the stats they are both 3v and the sizes are in mm
bat mA diameter height
AA 2800 14.3 50.5
123 1300 17.1 34.5
CR2 0750 15.6 27.0
2 of the CR2's wouldn't fint in the E1 body darn! A bit to long. They are just a bit thicker than an AA and quite a bit shorter. So if Surefire made an CR2 E2, it would run 1/2 as long. My guess about 25 minutes since it would be a big load on them. With the E2 there is a chance we will see a 100 lumen lamp, but if CR2's were used they couldn't take it.
You can usually cram 2 CR2s in place of a single AA (with a little work). I did this with an Infinity task light. I agree, it ought to be more commonly done. The lower charge capacity of the CR2 compared to a 123 makes it more suited to LED lights, but that's the other side of the forum.