You can have Chris @ flashlightlens custom cut/reduce down a hardcoat acrylic lens to a custom size of your choosing. For example select the 28.6mm lens and tell him you want that lens cut down to 28mm. For my L2's I usually go with a diameter of 28.1mm for a slightly snugger fit. Feel free to...
It certainly is different, I dunno if I would buy one though. My main concern would be the heat dissapation. There is definately more metal compared to a P1, but not a whole lot of surface area for metal to hand contact.
A good host that is similar in size to a D25LC2 would be the EDC 18650 , also available at mtnelectronics sold as a "S3". The NCSU033B has a max current of 700ma with a Vf around 3.8v+ (hard to tell by their datasheet). As for a driver the easy way to go would be a 2 X AMC7135 driver that will...
My Mag build I mentioned earlier is more of a starting point/reference if you wanted to go that route. Obviously you wouldn't be using the same battery setup as I did. You can run 3 AA nimh in a 1D adapter wired in series or a single Li-ion with the popular AMC7135 linear regulator drivers...