I'm a bit involved as I've seen this unit through my Recruit lately. To be honest, what occurs IC should be enough. After one blackmark you should not only ICly shapen up but look at how you can improve OOCly. You lost a unit before so you should understand that the CCA is meant for strong, well played roleplay.
I'm sorry to say this, but this would occur realisticaly if the Combine were to be there under such tight protocols and if not, more often.
I think it's perfectly legit and would suggest the unpk to not happen. Plus, you can always make a new character better and more interesting then the other.
Plus, it wasn't a blacklist, just a PK. (: