I don't know there's too many ways they could ruin it.
1.It would have to be an action adventure game for one, any other genre wouldn't fit. Maybe strategy but no one wants that.
2. The maneuver gear mechanics would be tricky convert to a controller and to have them run smoothly would be hard.
3. It would have to be extremely difficult since:
A). You can only hit the titans in one spot
B). The titans are fast and kill you in one hit
C). The range of just one titan attack would be too hard to evade with the size and speed.
4. The camera would be annoying to control because your constantly moving while keeping an eye on titans.
5. Teammates would have to be responsive and with a command system which would be too overwhelming to try to do while doing everything else.
6. There would have to be a gauge on how long you can use the maneuver gear since it doesn't last forever and you would die landing on the ground once it ran out or be killed by a titan while on the ground.
Not trying to sh*t on anyone's parade or anything just saying.