If only...
If it were that simple.
The UK climate is fickle. You cannot and probably never will be able to rely on good weather in Q mating season. (Unless you are in a sheltered valley near to the West Coast with the Gulf Stream).
If beginners want early nucs, either the queens have to be overwintered or you have to raise them in early Spring..
Overwintering makes it very expensive to keep Qs. Unless you use min nucs (highish maintenance), you need a 2-3 frame nuc. Lots of money tied up in bees and equipment. We are talking 10,000 to 15,000 imported Qs being replaced here..
Based on the BBKA membership, (and say 1/4 do queen rear) that's an extra 2-3 queens per beekeeper. Extra.
And then the producers have to be prepared to post them.
(I have done it as a once off.. You really need to be organised to do it on any scale)
Frankly anyone who suggests there is any likelihood of that happening on that scale within 5 years is not living in the real world.
This debate reminds me of a certain (prominent non beekeeping) person making promises which are never met and which are made in the full knowledge they will not be kept.