Could the system being proposed for HST be used to deorbit ISS?

Probably not "as is". ISS is already 15 times more massive than HST and may

Just let ISS get low enough and one progress could bring it down.

The hard part isnt bringing it down, just dont reboost wait long enough and its
down.....

The trouble is putting it down where you want it....

Not on top of somenes head....

Keeping it up is really the challenge.
Hey this is my opinion