The problem with unifying the parts into one download, is that the code is incompatible.
When MB started this, he made some "decisions" codewise, that didn't turn out the best ones. When the Part 1 reached the 5 GB, he used that opportunity and fixed the code, changed the UI, created the Characters list and a few other things...
After that, the Part 1 is completely incompatible with Part 2 and on... There are also changes from Part 3 to 4, that may cause the same issues.
Basically, the whole game would have to be remade in order to put it in one BIG file. While I sympathize with your ideas, I don't think that will ever happen, or, even if it "should" happen. That time, remaking a old game, could very much be used in the making of a few new ones...
So, in conclusion, I wouldn't put any hope in the "Unified" version happening.
Peace