Could probably use the 7-zip engine since it's open source and .vp files are basically uncompressed .zip files (how true is that? Is that actually the case or is it a different format entirely?)
Yes I know this has been answered already, but I thought I would clarify it some more. A .vp file is the same
idea as a .zip in that it stores a bunch of different files including their path and name (and uncompressed as was already mentioned), but that is the only similarity a .vp has with a .zip, how the data is actually stored is completely unrelated to a .zip file.
Regarding the other ideas, delta patching the game data is a endgame plan for wxL2. The delta patching of the .vps does have it critics as well though, and wxL2 is a
long way off. Otherwise, I agree with The E, tinkering with the .vp files is not a good idea, for the reasons that he already outlined.
Fury, I think having separate patch .vps for each the main vps is actually a very good idea, and probably the best middle ground, especially when subsequent patches are presented as rollups of all previous patches. That is, you end up with the original release .vps and zero or one patch .vp for each of the original .vps.