Now that's what I'm talking about Hiro! I already sent Milky a PM.
you might want to find some milky threads and get caught up on milky's situation before hand. last i saw, he has been having some trouble with his turnaround time for reasons unknown to me. simply put, some customers are not very satisfied...
i agree with everything kestral has said up there. the L1 is my favorite light, and ive done a considerable amount of research on them, as well as tinkered with them a little.
I have read of at least 1 member that used his L1 with RCR123, and eventually fried the driver. ive tried it myself with my 6th gen L1, and output is close to the LX2.
the optic used is optimized for XR-E emitters, and while XM-L, and XP-G will give it more output its different because the beam is not as focused anymore. and the beam is quite ugly in my opinion. actually, the beam of the XM-L is nice, but was too floody for me.
I have a XP-G2 in my E1L which uses the same optic, and i really like the beam it produces. ive experimented with XP-G, XM-L, and XM-L2, and i dont like any of their beams, and eventually switched back to a XR-E emitter. a XP-G2 with that optic produces a much cleaner beam though. while still having good throw, with a brighter inner spill, and the same fading outer spill.
swapping in a different emitter is the easier part. replacing the optic with a reflector is harder i think. the optic is 22mm in diameter i believe, and quite deep. many reflectors are sort of swallow, so you would need a heatsink for the LED/MCPCB to sit on to raise its height for proper focus with its reflector. and unless you can, or whomever is doing the work is experienced with cutting reflectors and such, its not a task that can be precisely done without proper tools and methods. ive looked, and have not found any reflectors that are made for an easy replacement for surefire's TIR optics. i might have found some that fit, but i never tried, and gave up the idea of replacing the optic with a reflector after trying it out with a XP-G2 emitter.
the biggest obstacle is the electronic driver. from my understanding, the high and low is controlled by it. while the tailswitch sends the appropriate current signal to the driver letting it know which mode to be in. this is the reason why when a malkoff M61 is used with a LX2 body and tailswitch, its low mode is not nearly as low as having the LX2 head. this is because (i may be wrong) the resistance in the tailcap is 10 ohms, which is not a lot. that 10 ohm difference tells the driver what mode to be in. and the driver is then what regulates the current for its high and low modes. the tailswtich drops the current with its resistor, but only to send the appropriate current to the driver to let it know what mode to be in. i hope i explained that without too much confusion... im no expert.
milky's mods requires replacing the driver to get the output, but i think he also mods the tailswtich with a different resistor for more ohms to maintain the low mode.
i think the easiest way to get the output/size/2-stage momentary that you are seeking with your L1, is to get a EB1-T.
other than that, the more cost efficient way is to use a RCR123. and if the driver goes poof, surefire has a great warranty, just dont let them know you were using a RCR123.
they might even replace it with a EB1 since the L1 is discontinued.