Yeah, I think you should spend more time looking over your options.
I think I'd meld a set of 421C wings to an AT-802 fuse preferably or a Drom if on a hard budget, remove the hopper and build a nice forward club seating with fold downs for sleepers. 4 seats with lav & Galley. Next is to fit the deisel burning Wankels that the Navy is using on their outboard applications, gear them down and swing long meaty props and potentially running 4 rotors. Have to move the gear in the wing, make the TW retract and clean up the plane overall as well as rearrainge the cockpit (they're pretty fair sized) for staggered side by side to allow pilot transfer down front to the cabin. I could build that for less than half a mil. If I had more, I'd probably just scavenge the gear out of those wings and build the NASA foil that the LanceAir IV uses, fully wet and which would have fold down floats/tip tanks and a retractable float molded to the bottom of the fuse. It forms the fuse and tank tucked behind the cabin and below the cockpit and empenage that goes down and forward on a set of parallel links to make it amphibious. On the left side of the panel goes the Chelton EFIS with terrain above an MX 20. A slim double stack of engine instrumentation to the right of that above the fuel management panel. On the right side of that is the radio stack with an MX 20, 480 and 530. The only add on I would get is the radar. On the very right would be a standard six pack with HSI. The switchology would all be set HOTAS or dang close to it.
300+ kt cruise, amphibious, deisel/JetA/JP4 burning non-turbine engine, legs to cross the Pacific (which means world wide range), comfort to handle sustained long range operations, well built for surviveability and streamlined for efficiency. There would also be the head turning factor.
But I haven't thought it over to much either.