I had a solo GS550 for a while, I should think it would make a good enough tug. The engine was pretty bullet proof though the electrical connectors and general wiring were no better than should be expected on a Suzuki of that vintage. The carbs on "yours" may just need a clean and a tune or it could be he found something nasty and wants rid quick.
A badly set up rig is an unpleasant and dangerous liability so take some advise when joining the parts back together.
For my next rig I would be more inclined to go with a more road biased bike (or even a crusier
) and get the advantages of stiffer suspension and lower centre of gravity. What you get should depend on what you will use it for rather than looks after all you don't look at it when riding it (you mainly look at the ends of the handlebars as you haul it round bends).