1st q: no
2nd q: no
there even is not enough space in the head to think about modding it to led,
battery size (sub-C) is really good with Ni-Cd, Ni-mh, but there is nothing with other chemistrys
(build Youself a batt stick out of newer 4000 mAh cells. With my older 3.500 mAh I get a 1 hour 20-25 mins runtime on the main bulb)
PS: as one Li-Ion is considered to be about the same voltage of three Ni-Hms, something like an 18650 could be possible.
But its a waste of space inside the light and I have no clue on the effect of