I'm not familiar with this particular plug, but I was thinking along the lines of poking a hole or cutting a short slot in it and prying it, distorting the shape until enough threads pull away or loosen that it can be popped out or easily unscrewed.

I'd imagined it might be similar in size, shape and thickness to a standard engine block freeze plug (only threaded in with perhaps a stamped hex head in the center).
But if it's smaller or thick walled I guess this wouldn't be practical. A hardening sealer is used many times on freeze plugs, if it was used on a threaded plug it certainly would be pretty hard to get out.