If you mean rules, then better rule systems are already out there. Which one exactly you want depends what you like (or hate) about GW rules.
If you mean the lore... open source lore sounds terrible. Not worth compromising your principles over, but it is a loss. I would not call it "easily replacable."
If Dave Filoni is put at the helm, I'd have hope. Not that they won't continue to offend, it's Disney after all, but at least hope that they'll still tell good stories while doing their pandering/social engineering.