I think the main problem you have is population numbers.
There are 17 english men to every one welsh men.
If you extrapolate those numbers to say the recent BSM qualifiers.
Across the 3 regional qualifiers in england you had maybe 45-50 guys compete.
Based on a 17:1 ratio that equates to less than 3 welshmen at their qualifiers! I propose a bit of a radical solution
Open up the welsh qualifier to anyone that hasn't qualified in their regional england/scotland qualifier.
Guarantee at that comp. the top Welsh competitor qualifiers.
Make the remaining place(s) up for grabs
It might mean you get a few guys from the south/north/midlands/scotland competing with the welsh for the remaining qualifying place.
It should bump up the numbers and make it worthwhile for the promoters.
At least one welshman goes through and others if they are good enough.