In blackrock all transmog are unlockable at 2450 personal arena rating so it mean the people who are in the range of 2500-3K rating dosent have any exclusive rewards.

The idea its to add new transmog for peope who have best arena stats such as 3k 2v2, so they can be recognized and differentiated from other players.
Also why in 2s ? Because its the bracket with toughest player only few players got 3k 2s meanwhile way more player got 3k soloq, so its more valuable.

Can also add transmog for 2.9 player and 2.8 player ofc.

This idea could add some new content and new reason to play in warmane and we all know the server need it as the activity is decreasing years after years