I have given thought to putting something like this together, but it would be quite difficult to pull off convincingly. I don't think it's possible to integrate all of the changes in the mono mix into the six-track—there are too many ways in which the mono version was remixed differently for that to actually work. Also, there are many additions for which there is probably no clean source that doesn't have other things mixed in with it, so they can't be separated out well enough. But a hybrid, which sounds like the 70 for the most part but has some mono changes here and there, would certainly be possible.
Really, there are two different methods that could be used for something like this. One is to keep it completely in upmixed stereo form the way it is now, just leaving in the '93 sound effects that came from the mono as well as splicing in bits from other sources. The other would be to use the '97 mix (which has many mono mix effects in it already) in discrete 5.1 as the main source, deleting the SE changes that don't belong. The latter method would be considerably more difficult in some ways, but possibly easier in others. Currently, I am unable to decide which would yield better results (with 'better' being a highly subjective term in this case, since we're no longer preserving original mixes but instead delving into the realm of personal preference), so I've never made any attempt to start such a project.
I only like some of the changes in the mono version. For example, C-3PO's extra line about the tractor beam is one I don't mind (I grew up listening to the '85 mix, which has this line in it), but "close the blast doors" annoys me every time I hear it. In one of the above methods, it would stay in; but in the other, it certainly would not. Maybe I should just do them both, to make things even more confusing. ;)