As small as possible, yet with features. Low mode with very long runtime, low enough that it doesn't kill your night vision, but still bright enough to see by, a bright high mode, and maybe something inbetween. With flat regulation in all levels.
I know, I don't ask much, do I?
I haven't received mine yet, but I'm honestly expecting the Jil Intelli to be just about perfect. The only possible thing more perfect would be the same features but with a Li-ion AAA sized battery. I don't think the L0P is too big, since I prefer narrow and long over short and fat; mostly the problem with the L0P, even your 3 level modded one, is that it'll always be limited by the battery. I wish they made 3V lithium AA and AAA batteries like they do with CR2 and CR123s, because we could make some really impressive lights with those, but I guess there's not enough call for them yet in wider applications.