Just to follow-up. I ended up sending the batteries to John Ritter in Florida. He had them repacked with fresh cells and returned within the week. Great service, very reasonable price (~$200/battery) compared to the other options that were available. Ritter does a pro job, the batteries came back better than new, with a guarantee.
Other solutions that surfaced -
Oppenheimer Camera (Seattle) - Marty designed and built an adapter/converter for gold mount/v-mount batteries that is elegant and beautiful, and very expensive (~$3,000). This is a very good long-term solution for the camera and I will definitely consider this next time my batteries go down. Marty says it will last 10 mags with a AB Dionic 90, which defiinitely outperforms the Arri batteries. He has one in stock currently (gold mount).
Cinepower (UK) - designs and makes their own Arri 416 battery and chargers. Theirs are NiMH which means they will be heavier, take longer to charge, and will have 'memory' issues if not stored correctly. But they will also last a lot longer than the Li-ion batteries. Also somewhat expensive (~ $2000USD for one battery and a charger). They don't have any in stock currently but can build them.
Do-it-yourself - at your own risk with Sony replacement cells (US18650V3) - will need soldering tools and a bit of electronics know-how.