Your biggest hurdle by far will be getting it inspected and licensed. If you plan on modifying the existing chassis, best bet would be to get it inspected and licensed before you do any mods. Around here, after it's licenced, DMV has no further interest.
The ones who WILL have an interest would be the insurance company. Most ask specifically if it has been modified...which may require another inspection. For instance, having 10 hole wheels but only using 5 would not get past even the most lenient inspection.
I would think buying a salvage running chassis with all the goodies you were looking at, and switch bodies.
Then, an inspection would be a breeze because it would only have to meet B-1-FA specs which it would meet easily. Around here they would use the body serial number for registration. They don't care about the chassis numbers.
There is still the insurance company to deal with though.