Well, since the new editor allow to place 7 Atr/Har/Ord Palace (and Atr.high tech) I've been thinking on ideas to use that feature.
For now I already used the Atr.High Factory on Harkonnen plus Harkonnen palace on Emperor to have both weapons striking the player at the same time, a triple Atr.Palace in my Tleilaxu Campaign, and a Triple Ord.Palace in my Spacing guild one.
Looking at your premise a fatal 4 way with those sub-factions launching DH each other seems factible :P.