Pb car batteries are optimised for automotive use and the alternators are matched. car batteries have many thin lead plates that will deliver, or take, a lot of current, even when very cold or hot and the alternators can recharge the battery quickly for lots of quick starts and stops in.the coldest weather, taxi/mom, winter, chicago,christmas,school as to reprograming, not so much, automotive "charge controllers" were/are designed around Pb batteries ,which are robust beasts with a high tollerance for momentary fluctuations, and as the primary goal is durability ,they are dumb devices I live off grid, and use a variety of battery types, and voltages, so end uo reprograming regularly, and have even gone as far as to do an alternator deleet on a w250 3/4 4x4 cummins dodge ooerated at the 45'th parallel, and only the solar pannels installed on the hood for electrical power, worked with some limitations in winter, but not for the faint of heart. As soon as sodium batteries are cheap enough to play with I will be experimenting, but do expect there tobe pecuiarities to there charging cycle, and perhaps limintations on high current discharge. The test will be getting a DI diesel to start in the cold, after say forgetting to turn on the fuel for 10min, having to then boost from a Pb battery conected to a BIG regular alternator, no fires or bieng "dissabled" allowed. So the real answer is that the whole automotive sector will have to be compatable for rescue and emergency services to function, not counting just normal "hey,gimi a boost" calls costing $5000 in repairs or whatever

I assumed they were a poor fit for the starter-motor problem, the need to supply super-high current (load) to get static forces overcome, swing the engine into it's cycle. But, I see they are capable of that burst of high load. So, indeed it begs questions.

I suspect the engineer approach would still be to demand a brick of standard lead-acid battery size, to fit into the hole, and the least possible change to wiring harness and associated behaviour.

Building out cars which need a different box in the hole would be something you do with supreme confidence it isn't making you awkward in the marketplace. If you wind up at the petrol stop in death valley with a dead battery, and alas a good ol' lead acid unit can't fit, that isn't cool. Battery replacement happens in all kinds of places.