I once had exactly that same tractor, with turf tires and a FEL. Best small-tractor I ever had probably. Traction in mud was not good, but I wasn't called to clean-up after mudslides very often.
. I really dislike R4 tires on a compact tractor because they're just bone-jarring (and I don't think a seat of any kind will fix that). R4s were designed for and belong on skidsteers. If you want a better ride, a longer wheelbase will make the biggest difference, but if there is a turf tire that the manufacturer says is GTG with a loader I wouldn't be afraid to try it at all. Changing rims if required will probably be expensive though.