If Nate Diaz is looking for a challenge as a free agent, Mike Perry is ready to welcome him to the sport of bare-knuckle fighting. After completing his UFC contract with a win over Tony Ferguson at UFC 279, Diaz became one of the hottest commodities in combat sports, a proven superstar who can sell fights and back up his words inside the cage or ring. While the most obvious choice for a next step would appear to be a boxing showdown against Jake Paul, Perry has other ideas, as does BKFC President Dave Feldman, who’s already said he’s pursuing…