Much of Mozart's solo piano compositions translate almost automatically for string quartet and classical orchestra (I know from having to do several at university). I do feel, along with several much better pianists than I, that Mozart's piano writing is very orchestral anyway, and by imagining how you might arrange it for orchestra, you can bring the piece alive to a greater degree. I wonder if he wrote such music with orchestral sounds in his mind.
As an arranger myself, I have had the opportunity of arranging piano music for ensembles from school orchestras to small professional ensembles, with varying degrees of success. It is the imposition of the parameters in terms of the forces available that makes arranging often slightly a chore rather than an out and out pleasure. I once had to arrange the wedding march from Lohengrin and a few hymns for descant recorder, oboe, classical guitar and french horn. Sounded ok, but not my first choice of instruments.