Special enemy variants in the Circle of Slaughters?

Why not have rounds where maybe 1 or 2 special enemy variants like Chubbies or Loot Tinks spawn in the Circle of Slaughters?

Like if on round 5 there was a wave where among other skags, chubby skags spawned and in round 5 of the slaughter shaft, a loot tink or two spawned among the other tinks in the beginning. Would be a cool addition to them I feel.