2x120 paired with single phase multiplus

[Gchaney]

I have a 24/3000 2x120 recently installed in my camper and would like a bit more power. Would rather not parallel another 2x120 and was thinking why not use a single leg multi 24/5000 input only on L1 similar to when using a generator. Curious if the community has any input why this may not work. I have a drawing but don’t see a way to post images on here.