-
You'd need some sort of inverter or USB charging pack - dynamos are AC out, di2 are DC in.
But you're right, it is possible. I was being facetious about the battery - my point was rather more it's still a bit of a silly choice for touring / packing. Battery life / charging aside, if anything goes wrong with any part of the charging / di2 system out in the (a) field, life might get very difficult quite quickly and I would rather a relatively simple and ubiquitous mechanical system to fix.
Admittedly looks like a Transco/enduro sort of rig so horses for strange courses
Edit; uses an igaro for charging.
I meant for the Di2