Well Had,
I think that your targets are farther than you think. While you can travel lots of places in a US built coach, people do this all the time. I also see European registered coaches in our travels on land. The cost is not trivial, but it can be done. You can also lease coaches at many port cities. I have classmates that have done this.
You are not the first I know to have been shut down by chemical sensitivities. Even if you change suppliers, the major components a still very similar.
If you don't like the motion of a monohull, then you might also consider that multihulls get less stable with "Theta"(angle of heal - this site can't make that character) and all have a serious stable 2 issue. Stable 2 being fully inverted and often has a better "righting moment" than does stable 1. They are also much more likely to break up in bad sea conditions. Having the boat leave you is a very bad day at sea.
From a naval architect, licensed marine engineer, boat builder and lifelong waterman
Matt