Or they can just create a new type of game.
MGOUG: Multi-Genre One Universe Game.
A game with a Fps, rpg, rts, strategy, board, card, moba, etc part. Kinda how a game would be a universe of its own and each game inside the universe as developpers/game designers assigned to it.
You wouldn't need to play the rpg if you want to play the fps. But, playing one would give sweet bonuses (mostly cosmetics or small boosts to X or Y) to the other games if you play them.
Ex: Winning 10 games in the moba with X champion will give you a boost to X reputation in the rpg.