I'm not going to say never, as anything with proper planning is possible.
With that in mind, while it is in French, I keep thinking in the past I have seen an english conversion, a blog about a french man that did what you are toying with in a Jeanneau Sun Rise 34. This boat was built between 1984 and 1989.
Alain Maignan fait son tour du monde - page 7 | alainmaignan.sportblog.fr
Some food for thought to add to the nay sayers, with a yeah vote/possibility