Sounds a good plan, Driz, but not strictly legal or course, except perhaps in Scotland.
I’ve suggested also the disabled symbol as a road marking for advisory bays in place of the text. But if the bay is later to be converted to mandatory when the order comes through, any such symbol or text needs to be removed and replaced with the legally correct version. Perhaps it could be done with a temporary adhesive marking to facilitate that.
The main legal problem with ‘advisory’ bays is that they often contradict what the underlying traffic order says should be there on that bit of road, arguably making adjacent measures unenforceable.