Except that any files added like skins wont be erased when prompted to overwrite, unless the name of said new skins is the same as updated skins
I don't see your point really... I know the update package will not contain my custom skins and thus if I do an Update via CM it will indeed retain my extra skins (and a Clean install will not retain them). But you suggested to copy over the content of the install package manually (not using CM) , and I say it is the same result as Update via CM.
The point I'm trying to make is this:
If it is a full package but some files are removed , and you manually copy over the files from the update archive into your content folder, the removed files (which the author deleted) will remain in your mod folder and not be deleted...
If it is an incremental package (just some extra files), then a Clean install will break the mod (so would deleting the folder manually and copying the archived content to your content folder).
You do not know what case you are dealing with unless you first examine and compare the downloaded archive content to what you have already in your content from a previous version, to be sure what it the right course of action.
It is time consuming and not logical that the author leaves this for all who downloads their update to figure out for themselves (or finding out through trial and error and having to resort to a backup in case a clean install was not the way to go, like Masscot suggests)
An auther should imho always with the release of the update mention whether a clean install is
a) mandatory (in case deleted files compared to his prev version.)
b) not needed (in case full package and no files were deleted compared to his prev version.)
c) prohibited (in case not a full package but only extra+changed files - eg. altered data.acd file or altered ini files)
Don't you all agree with this?? (I sure hope so , and that I'm not the only one who sees the logic in that...)