Given that the breach is by far the most valuable thing in Malifaux, it would stand to reason that the guild would have those whose sole purpose is the security of the breach as well as the railhead. Thus, my concept for you:
Rail Knights - Armored Close Combat specialists. They not only secure the breach and rails, but investigate and eliminate threats to them. Their armor is an ingenious steam driven supplement to already formidable skills. Further, that armor is a part of them, and as such is all but irremovable (think steam powered cyborgs... steamborgs if you will). While trained in the use of ranged weapons, they far prefer to be up close and personal where their armor and skills best suit them. While they are not fast by any standards as far as ground coverage they make up for it by being able to take it as well as they can dish it out... probably better.
That is the rough concept. I have some sketches that I will get up before long. And fear not, despite the steam power, they look nothing at all like war machine-esque characters.