If you do it completely ad hoc without an arrangement with them beforehand, yes, absolutely. But has anybody actually tried to talk with them about it? They might be very open to this for all we know.
Also, I don't see that much of an issue with it taking place it a different setting. It doesn't have to be Warhammer universe. The setting was never what made Dark Omen unique.
Honestly, even the system can be modified to make it independent of Warhammer. It doesn't have to be a clone, just "inspired" by Dark Omen.