re-sizing the overall dimensions of the PNG textures gives a small improvement to the load delays, but you should only experience these delays the first time you fire up the game without cache. My old laptop has Intel graphics in it, and i can play ff7 just fine in widescreen with all the graphical mods and very minimal hiccups.
Another avenue that was discussed was using the JPG format for smaller file sizes, but that was more to ease distribution of the packages. In the end PNG was chosen for its loss-less encoding, thereby preserving all the hard work that many of us have put into these textures. There was a lengthy discussion about this some time ago(wow, nearly 2 years!)between many of the members of TA and Aali, and this is what was chosen.
As far as ZIPing them goes, PNGs don't compress well. Give it a try, you'll end up with 15% compression with .7z files if your lucky! Even programs such as PNGgauntlet(another option looked at) don't make a large enough difference in filesize to justify the time it takes to run them(10-15%).
What I would like to see, however, is the "ff7/modpath/random directory/here are my mods" simply changed to a concrete "ff7/modpath/here are my mods". The /modpath directory doesn't support multiple folders inside, so it just seems weird to have it like that.