Do you mind if I pick your brain about something? How feasible is it to homebrew a BMS for a Lithium-Cobalt battery pack that's relatively certain not to burn your house down? I know not going with a BMS at all is a huge nono. Lots of people in the e-bike community have found out the hard way how difficult it is to manage a battery pack without one.

Cobalt cells always have an alarmingly non-zero chance of burning your house down, no matter how good your BMS is. Designing a BMS is a task for an experienced electrical & firmware engineer[ing team].