Trevor,
I would never turn down a 46 fixed window, rust or no rust. I think it just boils down to your time and desire.
Like an old school shop teacher told me, "a man put it together, no reason a man can't take it apart".
I am stuck on several things. Like, and I continue to bore people with this, "in the states, who fixes Renault transmissions and rebuilds Renault engines (to include parts)".
I notice the trans issue is rarely, if ever, addressed. Maybe if it isn't said out loud, nothing bad will happen.
Mike