Couple things to consider.
1. There IS room somewhere. Especially if going with more LI power. It’s low amp draw you don’t need welding leads to hook them up. Even if the supplemental batteries are 10’ or a bit more away from the connection point to your DC panel or existing battery box.
2. You could improve your quiet charging (presume solar because if you had a generator you likely wouldn’t have the same query).
3. You could add a big DC DC charger and use the Moho as a generator.
4. You could get a small quality inverter generator or even a cheapo bigger inverter genny for far less $ than what you’ll lose on selling and re-purchasing Battleborns. Probably be money ahead even if you purchase additional LI battery power frugally. Maybe even $0 cost if you find a nice used Honda or Yami genny at a decent price. The used Honda I bought 10 years ago is still worth what I paid for it. (Likely more…FJB)
5. You overpaid once for batteries. Taking a 50% hit on those to overpay again (Battleborn) is doubly silly.
6. If you really think adding only 25% capacity (200 vs 270A) will do the trick (seems like you’d be asking the same question again next year though…) then options 2,3 or 4 are easy solutions that may or will yield better results.
7. What do you “really” need? Your post alludes to a single trip that (idk what “after lots of research” means) presumably you either went lights out and the beer n burgers got warm or you had to curtail your power use to make it the whole time with cold beer.
You’re planning on this being a more regular occurrence in the future? If so, options 1 or 2 are your best bet. If not, see option #6.
In all cases option #5 is a very poor choice IMO unless you like showing off your trick overpriced batteries…..
Which brings about #8, which is actually a spin on #1. You could showcase your Grunt Style, military inspired high tech power supply in the camper. A little plexiglass cased 12V ottoman with quick disconnects comes to mind. Or maybe a Battleborn night stand?
And I almost forgot. Option #9, wholly endorsed but never sponsored by our very own expert @pianotuna. Scrap it all and go 24, 36, or 48V. On the upside you could likely do it for the same or less $ than that one new Battleborn big boy battery!
And finally option #10, serious about this one. Use your Moho start battery in a pinch and keep one of those little LI jump packs in the event you need cold beer a bit more than an engine that doesn’t need a jump start. You could even upgrade your start battery for not alot of money (in battle born dollars) and maybe only use the jump pack as a beer coaster.