I've no idea if this is even possible so go easy on me, but it'd be pretty fantastic. Someone got it working on Android devices a while back but that project seems to have stalled (not sure if they just got bored with it or something changed that totally broke it).
On the series s/x you can use a external HD but any next gen games must be on your internal ssd, or you can buy a ssd expansion card, but pricey. Any xbone, 360, or og Xbox games can be played from external tho.