(or, don't save, when nothing is changed)
My problem is I save unchanged files all the time because I can never be sure if I changed them or if I saved them, and trust me, it isn't just paranoia. This results in files changing for no good reason on my disk, and thence in SCM, or wasting bandwidth syncing to dropbox etc -- and that's due to the timestamps in the zip file.
If renoise knew nothing was different, it might not save. That would work for me.
But I'm also going to suggest something which may be easier: if the timestamp in the zip header and zip entries were set to some dummy value consistently (by an option, I suppose), then saving a file which hasn't changed would result in an identical file, thus avoiding the problems.
I'm also suggesting that because timestamps and serial numbers in files make me mad and I would choose any option to disable them, on principle.