Do the models in anyway represent the intended models other then weapons? Is the army painted? Does the army make a very good effort to keep the flavor of a sister army? Do the exorcists look like exorcists in anyway? Do the "not" rhinos other then the base have the same profile as a rhino?
If no to any of these comments please see below....
In a tournament I wouldnt want to play you with that army.. However thankfully for you that is not my call. I am sure Chase and Sam can better answer this.
It's gonna be painted (it's already basecoated). It's sort of analagous to Sisters, except it's "evil ghost daemonic sisters"... the vehicles (black coach anda cut-down Mortis Engine from the vampire counts range, etc) are longer and taller in some respects than rhinos and exorcists, but I'm fine with playing it that if the model gives me a disadvantage, I get the disadvantage, and if it would somehow give me an advantage, I'll play as if it were a standard model.
The seraphim and my Celestine are probably on higher flying bases than standard seraphim and standard Celestine, so I think that can only hurt me, and I'm fine playing with that additional pain.
I'm not using actual meltaguns to represent meltaguns, but the meltagun-toting models will be very obvious and carrying guns that look quite "heated".
Anyway maybe I'll just bring in the army to show chase/ben before the tourney to get the ok