I, too, would go with AGM batteries and not worry with watering lead-acid batteries and cleaning the sulfate. I wish I had done that much earlier on our previous coach as I got sick of water and cleaning batteries. I know that a water system could have been installed but they still would sulfate requiring cleaning.
Currently, we have a small fridge in the bay that has a small freezer for ice trays, etc. I keep three frozen ice packs in there to reduce run time. I set the fridge dial on 2 out of 7 and the frozen packs stay frozen and all the drinks stay cold. Seems to me that having something in the freezer keeps the defrosting cycle from heating the whole fridge reducing it's temp.
Our coach is set-up with 3 Lithium Ion phosphate batteries that probably replace 12-16 AGM's if it were set up that way. These batteries are expected to last at least 10 yrs. and can accept 30,000 cycles.
Lithium Ion batteries are not affected by low pull-down like lead-acid and AGM's. Regular batteries can be damaged taking them less than a 50% charge. Li can virtually go all the way down and be be brought back up without ill effects. Our set-up is set to recharge the batteries once they reach a 30% (genny will kick on). Our batteries can be rebuilt in the future further reducing replacement costs.
Back to the Original Poster.... I would go with the LP fridge if it is truly an option as that sounds like your best bet.
Safe travels,
MM.