Well it would certainly be a new interpretation of the butcher's apron. Personally I tend to regard it primarily as the Ulster flag, because the place you are most likely to see it flying is in Northern Ireland. I also associate the butcher's apron as a symbol of the unified armed forces of Scotland and England against common enemies, so yes I think Cymru ought to be there too because the Welsh have laid their lives on the line for the common military too. Its a flag I rarely see flown in Scotland or England (you see lots of saltires in Scotland and lots of St. George flags in the north of England). One of the few places which flies the butcher's apron is the aviation museum at Carlisle Airport, when we are open, as our museum is almost entirely about the Royal Air Force, and of course I take my turn of raising the flag there, always making sure it is the correct side up.