problem is to get the THICK heatsink for the led into a press fit to the head, so that this can act to cool the led.
Read a few modding guides and decide if You can build it.
the led has to sit onto an aluminium rod that should almost be press fitted into the larger hole of the head. Instead of the large part of the Light Assembly (these two metal plates with the black plastic in between), Your new "holder" can be made also from aluminium, or whatever material else, and could house a circuit (one for a single Li-Ion should work - I am thinking of this mod for some time now, but have never tried it)
There is a fair chance the hole in the reflector has to be widened and thats why I have not started this project.
If You really want, the 2nd hole could house a 5 mm led in direct drive (white, red, green, UV, ...) I would use a multimode circuit and leave this one free
PS: I agree on a good led run at 1 A seem brighter, dont use my 9N because of this reason. Anyway a batt stick made from a 3500 - 4000 mAh battery runs the light for 1.25+ hours ...