Two other things:
1. The Blood Ravens-Thousand Sons connection didn't become solid until the Horus Heresy novel A Thousand Sons. I understand Black Library has tried to distance itself from that angle since, but it was a rather blatant one.
2. And speaking of blatant angles/connections, I sincerely hope the decision is never made to disconnect the Knights Errant from the Grey Knights. I can't see how that would be accomplished without it being a contrived move, purely to throw in an unnecessary "Gotcha!" twist.