I'd be down with that. If BotW2 really does follow Zelda and writes Link and the Sheikah Slate out of the plot, it could be written in as some arcane focus Zelda uses to teleport.
Not really. If the game included an instrument, I'm assuming it'd be used as very predetermined points to open doors, trigger cutscenes, and bring gameplay to a halt. Stuff like warping can already be handled directly through the map in BotW, so I see no reason to include one.