Toy Hauler Bed Conversion

Not sure if this would work for the height & space between the 2 couches, but you could try https://www.samsclub.com/p/6-fih-bench-fold-in-half-bench/prod17220091?xid=plp_product_1_1

and then put a double air mat on top to even things out.

I'm not familiar with your trailer. I have the HappiJac Bunk Bed in mine. It's a good way to have a bigger bed. But the older I get the less I like it.

Having had a unit with opposing fold out couches I'm not sure how you would do it but anything is possible. Custom made though.

I haven't seen anything like the commercially. Doesn't mean you can't though. But trying to get it to be comfortable might be a challenge. You might look under the existing couches to see if there is a manufacturer name on them, somebody you could call. Finding a center mattress piece that is the same size and density would be the issue that comes to mind.