If it's the challenge .22 shooters are after, then surely taking on .177 shooters with their advantages must be a greater challenge. After all if challenge is everythying then 'silverware' doesn't really matter does it? Seeing how well they do against the .177 shooters should allow .22 shooters to guage their acheivements.
If silverware does matter then why not go to .177. Shooting with a .22 should have improved the .22 shooter's rangefinding techniques (and I suspect it will have too, I reckon, for example, Johnny Smith's rangefinding skills are up there with the best) and learning the wind is probably tougher with .22 (since wind deflection is mostly a factor of time to impact rather than weight or size of projectile) so .22 shooters should do pretty well.
Either way arguably, unless there's significant demand, there's not really a need for a separate class.