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).
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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.