The easiest option is to wire it just like it was an ordinary strat - in otherwords tape of the extra wires on the BKP and treat them like two wire pickups.
That gives you a pretty standard:
Neck HB
NeckHB, Middle SC
Middle SC
Bridge HB, Middle SC
Bridge HB
To me it makes sense to have the switch doing something simple that wont confuse people who use the guitar.
This simple scheme can then be added to with mini switches or push/pull pots.
I would be tempted to add a push/pull pot as a coil split for each humbucker if you are after maximum versatiltiy, you could use a push/pull pot that does both at the same time.
Extra settings from that =
Neck SC
Neck SC, MiddleSC
BridgeSC, Middle SC
Bridge SC
So a bit more classic strat sounds!
I would also be tempted to add a neck or bridge override switch as a push/pull pot/miniswitch. That gives you these extra options if you have a seperate coil split for each pickup
Neck HB, Bridge HB
Neck SC, Bridge SC
Neck SC, Bridge HB
Neck HB, Bridge SC
Neck HB, Middle SC, Bridge HB
Neck SC, Middle SC, Bridge SC
Neck SC, Middle SC, Bridge HB
Neck HB, Middle SC, Bridge SC
Thats 17 pickup combinations! and the beauty of it is that it can be done so the guitar still looks stock in most cases
You will still probably never use more than 4!