I don't have the Peak light, so no idea about it.
I do have A LOT OF Photon III's, either as EDC or in various kits.
The size is a BIG advantage (no excuse not to have a light).
BUT .....
If you don't EDC a Photon III or a Freedom Photon, my main concern for stashing some in kits would be the complexity of use under stress.

Not a problem if you use them every day.

Might be a problem if you don't or if someone else has to use the light in the kit. You want to make sure you leave it in the mode you will want to use it in an emergency. If not, I'm not sure you (or s.o. else) will be able to remember how to set in into the correct mode, under stress.

Another point about Photon lights : I had quite a few PIII with a battery drainage problem (after a few months in the kit, the battery was empty, due to a pb with the microchip).
Be sure to test the lights before putting them into your kits. And check them periodically, to be on the safe side.