Hvc can't be handled by the charger, as it can't see the individual cells. An aging pack will likely go out of balance beyond a 50ma balance currents control if pushed to it's final moments. Letting a cell past it's respective hvc requirement
Likewise lvc, a controller can't see individual cells. To try and make it work people avoid using the last third of their pack. A wasteful exercise for both capacity money and lightness.
As the bms must control the hvc lvc levels, a fuse won't do as it won't be quick enough to protect the fets in many circumstances.
You have it bang on, a simple unit people won't get themselves in trouble with is needed. The first time somebody gets it wrong, is the last time you will sell a board unfortunately.
I still like the smarts. $20 and does everything upto 13s and 60amps with additional cooling. They do need work though, the design was rushed.