If a tablet could be propped up in tate aspect and connected to a nice controller then you could have a mini arcade type of setup but that's not really mobile gaming.
This is what I have for both my Samsung Galaxy Tab A 8.0 tablet and Apple Mini iPad 2 with Retina Display tablet (circa 2014 + has 1080p support from the get-go) -- both have tablet carrying cases that allow for tate & yoko + the appropiate gamepads to play the mobile shmup apps that do support such bluetooth powered gamepads. Still better than having to be stuck with using the capacitive touch screen setup any ol' day, indeed.
PC Engine Fan X! ^_~