How about a Honda Gold Wing quad? Dave Hannigan just introduced a 2 wheel front end to replace the standard Gold Wing's single front wheel, which, when added to the usual trike setup gives you one large and luxurious quad.
I talked to Dave Hannigan of Hannigan Motorsports recently about what he calls his HRT Roadster. Dave sells quite a few Gold Wing trikes of the usual configuration but he just introduced a kit to add a two wheel front end to a Honda Gold Wing GL1800. It's a well engineered setup that looks like it would be a hoot to drive.
One of the first questions I had for Dave was about whether it was legal on the road and he told me something I wasn't aware of, at least 5 states currently tag quads for road use, Arizona, Idaho, Montana, Wyoming and South Dakota, all states with lots of wide open spaces and a long way from Washington, D.C. If companies keep offering well designed vehicles like these and some states will license them, why not? Dan does sell this outfit with the disclaimer that should the government decide it will not allow them on the road, he's not liable which is understandable.
Dan knows Keith Smith of GG Quad North America who imports the BMW based machine and he told me how the two of them had a lively ride down the road when Keith came by for a visit, and Keith thought the HRT Roadster really handled well, much better than he had expected, especially when you consider the size.
Although the front end could be put on the front of a standard Gold Wing to create a reverse trike and get around any legal issues, they found the position of the wheels created a slightly unstable setup which they still have to work on a bit so for now, the quad is the only option. The Can Am Spyder, in comparison, has the front wheels much further back compared to this setup and Dave is considering several ideas to get everything right.
Although Hannigan Motorsports will sell you this kit to install yourself they much prefer to sell the whole rig assembled, or if you insist on doing your own work, they'll provide the space for you to do it under their supervision.
The complete rig out the door is around $42,000, which, considering the price of the Gold Wing and all of the trike and front end pieces plus installation, sounds about right.
I think it looks pretty interesting and I would definitely like to take it for a run through some twisty roads to see how it handles, the engine would certainly have the power, this could be a fun ride.