Yes. All of the yes.
Real talk, though: how feasible would it be to do a partnership with other studios and do crossover content? For example, Valve teamed up with Bethesda to create the Space Core mod in Skyrim, and even the iBlitzcrank skin was done to celebrate the porting of League to Mac. How likely would it be for Riot to team up with another game company and make skins based on copyrighted content? There would be a huge amount of content to draw from, and the joint popularity of League, champions and other gaming icons would almost certainly guarantee great returns for everyone involved, players and creators alike.