I see several future problems with the change in the battery design.
1. I have purchased and received a total of 4 of the kits with a removable battery. Now that they have changed the design, I wonder how long the batteries will last before they no longer take a charge? one year, 2 years, 3 years? Once my batteries no longer take a charge, what will I use to keep the derailleur powered? Will I have used the derailleur so much riding my bikes that I will want to replace the derailleur with a new one before the batteries die?
2. With a fixed battery I see 2 problems. First, If you are on the trail and the fixed battery runs out of power you are stuck. No way to shift. - ride it home fixed gear? Perhaps carry some sort of power bank and sit next to the bike until the derailleur get enough charge to get yo home? Second, what happens when the battery no longer takes a charge? Can the battery be removed and replaced?