I've voted for Blackguard staggered, but I also think the Yardbird might do you.
I've got the Flat 50s and Yardbirds sets.
Now, I would go for Flat 50 for Johnny Cash and some of the memphis/stax, but Yardbird for Andy Summers and the rest of the memphis/stax :roll:
However! I understand that Staggered 55 BG is slightly less winds and therefore not quite as thick as the Flat 50. I've not heard/tried it, but that makes me think it would do a better compromise on Andy Summers, and would definitely be in a better ballpark for your other needs if the Flat 50 is too thick.
Country Boy I don't really know much about, but I think it could well be a possibility too.
So my 1st choice would be Blackguard staggered, followed close by the Yardbird (I understand this might be the closest "spec" to what Mr Cropper was using in the 60s? Don't quote me though :lol:). And I would also be open to someone convincing me that Country Boys was a nice middle ground :D
Can't help on the humbucker, or the pots, not had to cross that bridge yet myself - but I have heard people talk about 350 pots?
I'd be wondering about the capacitors too - I like my .047 on fender singles, but I imagine that would make a humbucker pretty dark on tone half-rolled off! I have tried .022, and it works with fender singles, but not enough tonal difference for me personally. You can also get .033, I used them in my Baja for ages, and it was OK, but I've recently switched back to .047
Hope that helps :D
And welcome to the forum!!