Exactly!
I could be wrong, but I think the infrastructure is all there:
Using language from the game:
Ta-da!!!
We already have events that include Kingdom or Troop Type restrictions locked in.
Defeating Level 500 with daily Sigils could unlock the right-hand panel in my first image. It would cost 0 Sigils, and include no Delve Chest as a reward (and therefore no chance of farming Shards or similar).