Increasing house battery bank capacity

[breal14]

I have an external 'tray' behind the genset which holds a single 27M group battery. I just got the coach and haven't pulled it out to really take a look. Here's the best pic i was able to snap with 3 bends of my wrist in ways it was never designed to go I'm fairly sure that it says CCA 600 and RC 160, but might be wrong. Based on the marker that's cut off in the pic, it's a 2022, so fairly recently replaced.

It's from BJs wholesale club and branded that way.
seems the re-sell interstate.

So, this is the closest thing i could find for interstate:

SRM-27 battery | Interstate Batteries

www.interstatebatteries.com

wrong colors, but the CCA and RC line up.
so, it's likely an 88ah battery.

not a lot, considering it's really 44 ah usable. and since it's 2 years old, at least, it's likely 40ah usable or less.

I need this to last 4 days boondocking. at least running the house lights and other basics. We aren't heavy power users. fridge will run on the gas.
Coach has been upgraded with full 12v led lighting. shouldn't draw very much.

What i'm not sure will draw a lot is the water pump.

I believe i can fit at least one of these lifepo4 high capacity/small foot print batteries like Amazon.com in there and immediately go to 200ah, 180 ah usable. effectively 4x capacity without doing more than swapping out the battery. If i can fit 2, that's even better.

I need to do more research on the other equipment to see if it can safely charge lifepo4.

after that, I'm thinking a simple solar array like 400 Watt 12 Volt Solar RV Kit
and set it up on a custom/home made frame to park next to my rv. I really don't want to roof-mount it.

Or, i'll pick up one of those brief case portable arrarys.