I think the Wampa's were meant to feature more heavily (deleted scene) which was in the original script which got cut for obvious reasons.
I think you are right that to avoid halting filming all together the Wampa cave scene was created so they could film Mark Hamill and his injuries as a way to explain why he had all the cuts on his face. And to get the location shoot done. But it was in the original script but was altered slightly for marks injuries.
There also seemed to be a sequence where Luke uses his Blaster after the cave?... Wether it was to shoot a probe droid or at the Wampa still pursuing even though he just had his arm chopped off... Or perhaps he nearly shoots Han who was coming to rescue him.... Someone on here might know though I have no idea.
I wonder if this footage will ever get released... or is it in Jambee Davdars building empire?
Trying to be helpfull found some good mattes from superman returns check these.
And this Finemolds' 1/72 scale Y-wing on a ice field hmmmm...
Is that the same models Ady is using? simply because I remember the scale factor... They look really good when put into a backdrop
this is the guys photo stream