The Tigers are renegades; they are part of the PLA because the opportunities for gain are higher than they would be fighting for the Imperium. This is a Devos IV PDF Mech unit that has been fighting orks in the ash wastes for years.
In terms of modelling, they are a little more chaos influenced than the Bloodcoats; they are mostly Catchan and Maruder parts. I was going to give the Bloodcoats the sentinels (they need a little manouver capability), but they are too chaosified, so the Tigers get to keep them.
So far then.
No HQ. Contemplating a 'counts as' Straken officer, as he would be more in keeping with their fluff than any apsotate cleric.
Troops: Two platoons of command squad and three squads.
Elite: Eight Ogyrn
Fast Attack: a pack of twenty chaos warhounds, a troop of three scout sentinals, a troop of ten rough riders
Heavy Support: a troop of three LRMBT and a BaneBlade.
So that's a heavy punch and a lot of early hitters. These desparadoes are the PLAs hammer.