The issue is trying to equate a certain motor to a certain skill set.
Not gonna happen. Fast guy always wins until he is out skilled. Skill is formed in experience. Experience comes from practice of laps and setup.
Exclude everyone faster than you, gets free stuff or can out spend you.
Not gonna happen. The whole hobby segment is too small to tell anyone you can't play.
This whole perception of "Stock" is way off. All motors are stock to the definition of the word. They are made and packaged as retail "Stock". When the word was first used such as "Stock Car", you literally bought the showroom model and made it race ready. A 426 Hemi was a Stock motor. Modified was the special stuff you had to go to a custom shop for. Now all the two words mean are the same, specification (spec). That's why we spec the class by motor.
We classify racers by:
Pro - someone pays them to race.
Sponsored - Someone gives them equipment to race.
Sportsmen - Old guys who know how to race and don't hack each other.
Stock - everyone else with experience racing.
Novice - novice.
I think we're all just racers trying hard to find a win, but with different tastes for equipment. We come in all shapes, sizes and ages.
So to answer the original question:
21.5 will never and always be the new stock if that's what the majority wants.