As a burgeoning editor, I've taken one or two professional productions - Star Trek Insurrection
, for one - and recut it as an exercise for myself. But I've never shared that work nor do I intend to.
Recutting fan films is a whole other ball of wax. These productions are done in the spirit of fun and for the people making them to learn and enjoy the craft. Recutting their efforts for your own purposes strikes me as needlessly selfish and skates into douchebag territory, and is a slap to the face of the hardworking fans who produce this material for us.
So, in other words, don't do it.