I have the P7, and I want to mod it very much. It is an excellent body and it is not utilized at all. As previously mentioned it is extremely hard to mod.
The emitter is sitting on a post and needs to be large so it can be soldered to the wires. The main emitter is XRE I think and it has a rather large package. Some people have cut the MCPCB to some size and then inserted inside and wired up. Difficult stuff. Further complicating with array leds inside is not wise according to me. The body does not need such power, nor can it cope with the heating. The best emitter would be XPG3 5000K 90+ cri, or a Nichia 219c direct driven.
The battery compartment is also very proprietary. And it is notoriously difficult to mod. Horrid stuff.
This is why after the P7 all my lights are easily modified with off the shelf parts. I know the P7 is one of my most beautiful lights, and I would love to have it with a lithium battery and a powerful emitter. If you somehow manage to succeed in modifying please write up.
P.S. Here is my thread a few months ago, with no replies… Led Lenser P7 DIY Ideas?