I built an electric seated scooter / moped and configured my own BMS, using repurposed electric vehicle batteries. The BMS is inline on the minus side. So if it breaks, there is no circuit. No more using power from the battery or charging it.
These kind of machines only have their BMS, there is never any redundant functionality. And hundreds of thousands are being built like that.
Just focus on the charging voltage. Because that equals how full you charge them. And that should NOT be 100%. Because storing them at 100% for long time is not that good for them.
Just put the voltage at some State of Charge voltage a bit below, like 90%. You can ask them what is a good voltage, but it still has to be a voltage where the cells balance.
That is more important for a car that sits a lot of times, possibly in the sun. Unless you are going to travel in it for years on end, sitting still 100% charged is doing the most damage.
That is what I did with my scooter, to get the longevity.
Your main inverter should cut-off before the rest does, and you will be able to configure a cut-off voltage in there.
The rest you can just connect. The deeper you discharge it, the deeper the cycle, the more wear it is. You can make it really complicated for yourself, but if these batteries are properly used a small portion of the year, than just use it to the bottom.
Two cycles in which you deplete it to 50% do as much wear as one cycle where you deplete it to 0%. So it is not like it is super dangerous to go near the edge.
So if you needed the energy, it is good that is available to you. In the end it is there to serve you.
Again, the same with my scooter. I try to avoid running it down to something like 10% state of charge, but if I ever get in that position (which has happened), then I am happy that I can use that remaining energy in the battery.
Would I do that on a daily basis throughout the year, yeah, it would wear out quickly. But that is really about general wear on the battery, more than the exact depth of discharge.
If you are going to use this every day of the year, then yes, make it cut off a bit earlier, so the discharge depth is not that high every day.
If you are using this setup only a few weeks in the year, then it is far more important to not have it sit at 100% all the time.