Unfortunately this is something that Blizzard objects to. In a post on the Overwatch forums, the game’s director Jeff Kaplan said that the team is objecting to use of keyboard and mouse by console players. While Kaplan did not specify why, using a keyboard and mouse compared to an analog stick for aiming is arguably easier, and console gamers who aren’t using that input method are essentially handicapped which makes it unfair.
Also given that sometimes it’s not easy to hook up and a keyboard and mouse and get it up and running on a console, it means that console gamers who aren’t familiar with the technical know-how are left out, which once again is a bit unfair. According to Kaplan, “We have contacted both first-party console manufacturers and expressed our concern about the use of mouse and keyboard and input conversion devices.”
Kaplan also stated that they are asking console makers to either disallow mouse and keyboard conversion devices entirely, or make it so that using a keyboard and mouse is open and easily supported for all players.