"I have lots of things on the plate now, but yes, rechargeable battery packs for Series I/II is on my to-do list."

I want one.

Update: I ended up building both the wireless belt box AND a pedalboard input box, which lets me use any of my basses, including the Series I. I posted a few pictures for those interested here:
https://www.talkbass.com/threads/alembic-club-at-talk-bass.867548/post-29028041