There are very old two-output LNBs on some Primestars where one out is Vert and the other is Horiz only.
After hooking those two through a 2x4 or 3x4 multiswitch, you would have four outputs available.
There are also some other Invacom with linear output only . . . no, in retrospect, the only Invacom that's Standard, is the QPF-031 you mentioned.
No solution there.
Depending on the polarity needed by the DirecWay equipment, would a Dish bandstacked LNB work?
Actually, I'd be uncomfortable mixing my FTA with any other service.
We routinely discourage trying to integrate it with DishNetwork or DirecTV hardware.
I think there are better solutions than mixing FTA with DirecWay service.