Not sure if you know this or not, but I frequent some bits websites to totally customize my squads. The Warstore is an EXCELLENT bits site. They provide a GW bits trade in program that you can get store credit for. They also sell numerous historical, fantasy, and sci-fi figs from various manufacturers. The place is essentially a gold mine for any converter or painter.
That being said, I am completly ok with other people using other manufacturer figs. But with this comes one rule of mine, the model has to be as close as possible to a 28mm scale. I say this because some smaller models gain additional benifits in DS because of our use of TRUE LOS (cover saves, hiding and the like).
Adeptus Astartes Commandments
1. Thou shalt not replace the Librarian's staff with a magic wand.
2. Though shalt not refer to thine brethren, whom the Emperor has dictated be armed with an incendiary weapon, as a "Flamer" constantly. For this has been proven to lower morale and cause strife within His Most Holy showering facilities.
3. Thou shalt not follow a Librarian around thinking, "Can you hear me now", repetitively in an attempt to drive him insane.