So what's the design concept? Tzeentch magic everything, which wouldn't work in BB without a ton of special rules unfortunately. But they used to split, and even did so in BB, which is awesomely cool.
So lets do that.
Tzeentch Team
0-16 _ Pink Horror _ 70K _ 6337 _ Big Hand, Regen, Split, _ GM (SAP)
special _ Blue Horror _ n/a _ 6237 _ Stunty _ n/a
RRs @ 70K
No Apothecary allowed
Spilt (Extraordinary)
When hurt, this player spilts into two smaller blue versions of himself and carries on playing. If the player is ever KO'd or Injured then move it to the appropriate part of the dugout as normal, but also replace him on the pitch with two Blue Horror players as describe on the team roster. One Blue Horror should go in the square the Pink Horror has just left, and the other will appear in a random square adjacent to it using the Scatter template. If this random square is occupied, keep scattering from the new square until you roll for an empty one. The Blue Horrors will be standing when they appear, and their creation may take a team to more than 11 players on the pitch without penalty. At the end of each drive all Blue Horrors on the pitch or in the dugout will reform into their original Pink Horror, and should be removed from play. The Pink Horror should have been in the dugout and is then treated as any other player would be, and may be set up again if he passed his Regenerate or KO recovery roll. Blue Horrors are always rookies, and do not know any of the skills nor carry any of the injuries or special play card effects of the Pink Horror they replace. Blue Horrors cannot earn SPPs and cannot be awarded the MVP award.
Fun, fun, fun.

Does the team need anything else? Positionals? A big guy (Screamer/Flamer/Daemon Prince/Spawn)?
Joe