Looks great!
Yeah, that crossed my mind too, hehe. Careful with that; better wear goggles and a leather apron. But I can see the benefit in using a machine for this.
Hand grinding a plate of glass, is not a long process or vigorously done and, as long as you wear a eye shield or mask to stop yourself from rubbing compound into your eyes, you're pretty safe.
You could also put a large 'finger bowl' of any size, at your table or bench, that will allow you to soak the material and glass particles of your hands, as needed, and ALWAYS before moving to a smaller grit, it's no big deal.
It's not necessary to motorize the process, as an oscillating tool will generate dust and you don't want that!
Think of the possible consequences of having that dust on you sleeves/arms and other body areas, clothed or unclothed, ie. Tee Shirts and Shorts or no shirt in a too hot summer day or boiler room, that also might find you working them into your eyes, around kids and pets.
This stuff is not food grade subacious earth and it's also bad for your lungs and others.
Just for the fun of it, try using a Japanese grit of 8000 or one half mu first and go up from there, you might just find a usable glass faster, as the starting at the larger grit just breaks the plane of the surface glass, and those larger abrasive's scratches have to be removed by the smaller component grits, and there's no point in all that extra labor to get what you need.
IMO
