I just changed the cells in two 2014 Bosch 400Wh batteries, some time ago I did the same for a 500Wh. I just solder another battery in parallel on the BMS (just + and -, not the phases) while I disconect the battery I have to change the cells on. Before that I put it down at 35,4V as the new cells I put in are at 3,54V each. We bought an adaptator from https://dokteraccu.nl/
that alows us to test the capacity of the batteries, and to bring them to desired voltage
The cells in the 400Wh are samsung 29E (LG before that, I don't know the exact type), and in the 500 Wh I think they were Sanyo's but I'm not sure anymore...
Unfortunately I don't own any smartphone to put you pictures of the BMS, but I'll try to "stole" my boss's one or to bring my camera.
I already repaired several batteries from Bosch without any problem, from the old type or the new one. But if the BMS is out, the battery won't work anymore and you will have to pay the 700€ to get a new one