Hi Neels,
I do like the "DRAFT" marking as it is not a set of released manuals for a given version of the software.
Having said that, if there's a real benefit from disabling draft marking, please simply go for it.
If we ever have a set of "stable" documentation for a given version of the software, we can think on how to properly mark that version on the title pages of the manuals at that time.
I don't think it's useful use of our time trying to find other methods that enable DRAFT watermarking.