With 850 e-start, you have only the starter and battery. Starter mounts to motor. Compared to poo, no added primary ring gear and the heavy steel poo bat box and frame are eliminated, starter is smaller. One heavy kit on a poo. If you want to not pull start an 850 cold at the lightest weight, a LiPo with e-start on the 850 is the best option.
Shot has to start the motor within a 1/3 revolution or so from my understanding. This would be difficult on a cold start, so charging the cap externally may not be an option. If it was, with a LiPo jump pack through a port, you could possibly be able to cold start in a trailer (or anywhere if the carried the jump pack with you). I'd guess this will evolve more, tho.