How many mods can I do to one humbucker?

Re: the title of the threads.

If we're talking just the two coils and some switches, you have exactly 6 possible configurations:
One Coil,
Other Coil,
Both Series, 
Both Parallel,
SOoP,
and POoP.

Now, with the two coils as close together as they are found in a humbucker, both OoP options are going to be useless.  Even when the coils are further apart these would be special effects type things.  In an HB the signal will be so quiet and thin - and obscured by noise - that you'll never use them.

So we've got only 4 meaningful options.  There are various ways to achieve them.  It can be done with a single DP4T switch, or a couple DPDTs, or whatever.

Now, if you can afford a capacitor or two it opens up another possibility which is sometimes called Half-Parallel or Broadbucker.  Basically you wire the two coils in series and put a cap across just one of them - let's call that one Coil A.  Coil A has its highest frequencies shorted (like turning a Tone down to 0) but the high freqs from Coil B find it easier to go through the cap than through Coil A, and are therefore not rolled off the by the added inductance.  You end up with a hybrid sound with the highs of an SC and the lows of an HB.  The cap value here will depend on the specifics of the pickup and personal preference, but standard tone cap values are a good place to start your experiments.  

Theoretically, I think, an inductor could go in place of the cap, but I've never heard of it being done, and don't know what it'll sound like.

There's also a similar thing where you can get Half Out of Phase, but I think that too would be less than exciting in the context of a close positioned pair of coils.

I've never run across a 4DPDT switch. Is it an on/on/on switch? Is that the middle part of the Wolf schematic, that 9-terminal switch?