If you could find a 6P3T switch, you could wire them up to switch the way you want simultaneously, but I'm not sure if something like that exists. You could use one 4P3T switch (which are readily available from various sources, i.e. AllParts, WD, StewMac etc ... (4 pole on/on/on) ) to switch 2 of the pups simultaneously, then a second 2P3T (2 pole on/on/on) to switch the other pup. That way you eliminate one of the 3 switches. Bear in mind that the more terminals on the switch, the larger physically it is. You may find it easier to fit 2 or 3 smaller switches in the cavity than one big one. You could then route the "hot" wires coming off of your series/parallel/single switch(es) to the 5-way as normal.
Coil cuts on an Hb only need one pole, traditionally, just to shunt the centre link (red/white in SD colours) to ground, bypassing one coil. Or, to avoid shunting, the pole goes to ground and connects either to the usual ground wire of the full Hb, or the centre link connection. Either way three such single pole switches may be substituted by a 3-pole switch.