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My very first version of my BMS was going to operate quite similar to the way that LVD worked. The problem is you can not use voltage as an indicator of when a lithium battery is discharged, at least not if you want to put any resonable load on the battery. Voltage sag varies depending on the load and temperature. You'd constantly have to change the detection voltage based on both of these variables which would be quite difficult.
There are people out there with EVs and no BMS. They basically become the BMS by monitoring things all the time and making darn sure they don't discharge too far. They set their chargers to be very conservative on charging as well. They also normally oversize their pack quite a bit to give the the buffer on the charge/discharge they need to avoid damage.
So, it is doable, but its a PITA. I did it for a while with the PHEV kit on my Prius and the cost of the BMS is worth it to me.
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