First off,
to our group. I think by now you see that there is tons of top-flight knowledge here that will let you achieve your dreams in terms of working on your TT (travel trailer).
Not from me, by the way, I am no expert BUT, I do want to say this:
Here's a crazy idea: why not just clean it up keeping the original design, and just get on the road and camp in it for a while?
I mean, even that will be a big chore in a TT that has suffered some flood damage, since I imagine you would need to replace the floor, remove the lower inner panels (which means removing all the furniture and appliances) so that the by now rotten-smelling filthy dirty insulation in the walls and under the sub-floor could be removed and replaced.
You just might find THAT a big enough job!
If your interest in a total re-build isn't satisfied by that, you would have at least had a chance to look at the other existing AS floor layouts, and see which one could be modified to suit your ultimate design desires without becoming your life's work.
After all, you ARE buying this to be able to get out and camp, aren't you...? I bet your family is, assuming you are married with children.
In any event, good luck with it, and I hope you can get clarity on what it is you are really wanting to do.