As a matter of fact I used the original 2.0 track (of the Blu-ray) to test the Dolby Upmixer in my first Dolby Atmos AV receiver in 2015 and liked it better than the IMHO pimped 5.1 remastered track.
However, the original soundtrack isn't really something to write home about, its shortcomings become rather obvious during the first crew briefing scene and suggests that the source recordings themselves are in a rather bad state, i.e. I'm not aware whether there is technology that somehow could improve the original recordings.
The film was released in Dolby Stereo, so we did have the original Dolby Stereo Matrix with three separate front channels (L, C, R) and one mono-channel for both surrounds which is what Dolby Surround Pro Logic extracted from the 2.0 signal.
In this regard the upcoming UHD Blu-ray constitutes perhaps some improvement, i.e. it seems that the Center and Surround information is no longer encoded in the 2.0 track but for the first time both channels are available as discrete channels!
(4.1 = L, C, R, mono surround + isolated LFE channel)
I guess that's all the improvement we can possibly expect - and the upmixer in your AV receiver now probably has 4 discrete channels you can upmix.