I saw one of those today that had been converted into a three wheeler. It looked a little silly.
Different strokes. Riding on three beats the hell out of not riding at all.
One of my riding buddies lost a leg to an IED. He has a triked GL1500 Goldwing and hand controls. He couldn't ride without the third wheel. A lot of older riders trike up, and are able to keep riding. When the day comes, I may convert mine.
For my money. the 'Wing is the best bike to convert into a trike; it's a tossup whether the 1500 or 1800 is a better platform. I read about an GL1800 that was going strong at 250,000 miles, and a 1500 with more than 500,000 miles!