Any problems modding a PT Apex Extreme to run on 18650's?

[tack762]

Hi Folks,
I've been wondering for a little while on the possibilities of modding a PT Apex Extreme to run on a remote battery pack of 2-4 18650's. So I thought I would ask the wise ones of CPF. Does anyone foresee any major problems with such an endeavour?

Also, are there any better LED's that can be swapped for the 200lumen model, or is that pretty much it for now?

Thanks in advance.