Seems like your client wants some magic
Back in the days, before we had Object IDs we would use simple surface shader with flat colour (read emitter in Maxwell). So basically if you would make another render making your object behind the glass shaded as a flat colour (bright red would do) you could easily isolate it with all it's refractions - since its a simple flat colour. And if you would pick one of the three primary tones - you could even do that automatically with shifting channels in pretty much any compositing app.
I know, a bit of an old school approach, but if your client want's magic and you don't want to involve programmers - that's the easiest way to do it. Should also work on sequences