I think it would add something if somebody managed to integrate the Yoda/Lightsaber footage seemlessly into ESB (Probably not for this edit). At the point we see Luke fight a full-on duel with Vader, all we've seen Luke do with his Saber 'in anger' (In the previous 4 hrs of film) is vaguely wave it at a Wampa in terror (And have a trippy dream about beheading Vader).

We don't really see Ben teach him any fighting skills and then we don't see Yoda teach him anything either. Sure during the Bespin Duel Vader is toying with Luke to a certain extent. But Luke does make a valiant stand against him e.g. knocking Vader off the freezing chamber platform and slicing up his shoulder.

His sudden leap in swordfighting ability is never explained, but he has had alot of time to practice on his own, between the two films. But in most movies we'd be shown a little of that so we're not forced to fill in huge gaps in the narrative with our imagination.

It's not a problem, the film is fine the way it is... it's just an avenue for these projects to explore.