If you go #2 - here's an example of reasonably priced 300a ABB SACE S5 with 3 poles and 24vac or 24dc shunt-trip coil for ~$230 -
https://www.ebay.com/itm/285404101711 These ABB SACE breakers are hi quality especially if you're after hi amps (300a, 400a, 600a) BUT... there are many variations of amps, # of poles, shunt-trip, ABB SACE SX models and related price differences as they come on/off ebay all the time, so if you have patience for a good price you can do well for a higher amp shunt-trip solution.
Some use 2 poles for the battery + / - and the 3rd pole to disconnect the incoming PV charging current to more completely isolate current in/out of the battery.
In terms of shunt-trip / voltage - you want to see this sort of thing in the pics or confirm before buying as the shunt-trip coil may or may not be part of the breaker model number and even with a shunt-trip coil, there is a range of voltages. This one shows clearly it's 24vac or 24vdc.
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The often have auxiliary relays to trigger down stream stuff - maybe that would suite you're thinking somehow to trigger individual battery breakers as well? Not sure why, just pointing out the feature
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And just FYI they're super heavy - like 10lbs?