Also for our purposes young = 25 and younger.
Unless you want to play a little loose with the affiliations, like counting Shida (who's more IR) and Mio (who's freelance) then OZ Academy has no one who's under 25
I'm not counting the other smaller promotions as they don't really have a lot of younger talents.
If you include their regular foreign stars, Diana has quite a few.
Anyways, I guess i'd rank Sendai at the top of the list, though it's hard to look at Dash & Sachi as youngsters when they're 7 year vets.
After that Stardom, JWP, WNC, WAVE (most of their roster ain't as young as you'd think), Diana, Gatoh Move, IR in that order