The raised foundation is a killer when it comes to buyer appeal.
I would have to disagree with you on this (with caveats). I have lived in both raised floor and slab foundations. I prefer a properly built raised floor foundation. Plumbing repairs in a slab foundation can be a nightmare. When you buy a house built on a slab foundation, the state of the plumbing is an un-inspectable potential black hole.
I think what does turn off people on raised foundations is floor flex and noise. This has much to do with how the floor was constructed. I don’t know what the specs on the modulars are. The spacing on stick built depends upon span and spacing between joists. Unfortunately most construction tends to push the spacing to the limit. Closer spacing and larger joists (in the vertical dimension) make a tighter raised floor.
There are also issues with large tile/marble floors on a raised floor foundation.
