Depends on how much clearance there is and how much protrusion would be used to make an extended battery.Protrude down from the downtube? I suspect not: that would get in the way of the suspension travel of the fork.
It is the same integrated battery that is in the new UCP. You won't get odd size batteries because one of WW's goals is to used standardized components so you are not locked into buying replacements from them.Thanks,
I assume that is 14s 5p with 70 x 3.5Ah cells?
Could an extended battery that would protrude from the frame somewhat be a (considered) possibility?