Is there a workable solution, like a suitable backshot of the ROTJ helmet that can be matched into position and have the general profile of the reflections mapped over it?

Some might say with some justification that it doesn't really matter but it does highlight how many corners were cut in the making of ROTJ.

Would it have cost so much to film anyone against the window for a unique shot?

It would be nice if we had a similar shot of Luke meditating on the future like he does in ANH.

The PT sets this up as a family trait but maybe Yoda's teaching has beaten it out of Luke.

If not it might be nice to start a Fan-O-Matic style Dagobah sequence with Luke outside looking up at the sky and then over to Yoda's hut before him going inside for Yoda's death scene (which might be adapted from the lights fading sequence in the theatrical version).