Thanks for your answer.
I have to say I'm confused, as I did some testing and found out that wyUpdate will download the update "all.to.C.wyu" in the case I mentionned.
To reproduce, I did create a version A, which I installed on my computer. Then create a version B (+Update A to B, All to B), Remove the version A, and create a version C (+Update C to B, All to C)When starting application in version A, wyUpdate (Or at least the automaticUpdater) will check for a patch from All to C.
Anyway, I did disable the compression for now, which is not required for our acceptance version (We can now deliver test release much faster, as I found out it was that part which was taking time)I'll probably re-enable this when reaching production.I kept the "catch-all" update, because without it, I need to keep track of every version used up to some point, which is not possible in our case (Lots of user, which can stay up to a month without using/updating the application, and it's not an option to tell them to re-install the newest version manually)