I'm actually pretty desperate to see all the scenes that were filmed and that aren't in the film - whether it's parts of film scenes that were snipped for time, or scenes that were completely kept out of the film. I've got fingers and toes crossed that a Collector's edition BBM will include such scenes.
But, I do not think I'd like to see them added and inserted in the film itself. I want the scenes to come separately. The film is as near to perfection as it's possible to get it - the deleted scenes might too easily make it less so, since it's hardly possible to imagine it going the other way.
For one thing, several scenes that we know have been filmed would make the film less ambiguous and subtle, should they be reinserted. For instance, the second flashback and Randall getting out of Jack's car with those guys from the trailer watching, would go a long way to removing the doubt concerning Jack's fate.
Other scenes might change the mood of the film. While I'd absolutely love love love to see the scenes with innuendo and banter between Ennis and Jack, including the hippie rescue scene - I suppose that *would* break the slowly but surely mounting mood of gloom and frustrated longing.
Also, some scenes may not work for reasons we don't know till we've actually seen them. Nothing more than a tone of voice or a slightly odd facial expression may mean they don't fit in with the rest of the story and characterization.
Scenes that I'd most dearly like to see? Jack giving Ennis a gun and Ennis refusing it, immediately after the "I brought beans" scene. Since there are pictures available from footage from that scene than isn't in the film - as already included in this thread - I hope the gun-giving was actually filmed too. It was in a late version of the script, at any rate. Jack and Lureen rescuing the Malones after their car broke down, though I don't know if that was filmed - because of a line of dialogue Jack has there. And *any* scene of J&E hugging and being affectionate at the beginning of their final meeting - there are pictures floating around of that too - and I NEED to see that.