Was thinking more about this while reading the thread on Alaska Towns/Cities? - #10 by jpbari
Not sure how easy/hard it is but perhaps Wales is actually best suited to be at admin level =6 and only go to 10 in certain cases as a nested city.
If you look at the bigger cities in Wales then they all sit sensibly in 6 in OSM.
Eg Cardiff - probably makes more sense than lots of smaller areas like Heath that have 117 roads only
Newport
Swansea
It would leave some very large areas like Monmouthshire that would be very hard to complete. However, this part of the country is quite sparsely populated and this would get the roads in where there are none currently, and could then add specific areas at level 10 if required/requested (as is currently the case)