We don't have a lot of car makers and we do not have a huge amount of EV models.
Either you are doing this on small scale, than you can select one or two specific EV models and use these batterie packs or you do it in big scale, than you can also easily adapt the most x batterie packs and only use these across your system.
If you go down to the cell level, its more effort true but then you probably only handel cell types of a handfull of manufacturer again.
You can't really mix different types of cells together in the same pack. Even cells with the same manufacturer and chemistry can be problematic to mix if they are at different wear levels (or even from different batches from the same factory).
This is only practical if you reuse the whole pack, or at least the modules. And for that to work well you also need a lot of complex software to keep the packs working well with each other (like balancing power levels between the packs).
BMS software is no joke, it is already hard and complex enough when using brand new battery packs and cells of the same chemistry and manufacturer and wear level. Any kind of mixing massively increases the complexity and safety concerns.
We don't have a lot of car makers and we do not have a huge amount of EV models.
Either you are doing this on small scale, than you can select one or two specific EV models and use these batterie packs or you do it in big scale, than you can also easily adapt the most x batterie packs and only use these across your system.
If you go down to the cell level, its more effort true but then you probably only handel cell types of a handfull of manufacturer again.