The Strat with 4 P90s was a joke, as ashcatlt noted. But as the only one hereabouts who has (to my knowledge) actually built a 4-pickup guitar, I may be able to offer some ideas and/or help. Here is an in-the-works shot of my "4 Caster", which is now finished and playable.
Here's a link to the build thread, with wiring diagrams:
Now, you mention the use of blend pots. The only change to this from the photo above is that the photo was taken (as a mock-up, the guitar had yet to be wired or fully assembled)when I planned for three pots, V and T, plus a single blend pot to blend the two pairs of pickups. In the end, I scrapped the blend pot, as it didn't work the way I wanted. The problem, I finally worked out, was that there was simply too much of a load with all 4 coils operable when the blend was in the center detent position. The drop in volume was noticeable as one blended from two coils to 4. In the end, I scrapped it for a three-way toggle switch fitted into the center tone pot hole, between the V and T.
The theory behind this is that the 4 pickups are "mated" into 2 pairs. Instead of N/M/B, I have N/M1/M2/B. N mates up with M2; B mates up with M1, sort of an "overlapping humbucker", if you will. Each pair is controlled by 2 mini-toggles, allowing for each pickup in the pair alone, or both in series, or both in parallel. Then, the two pairs are united by the 3-way toggle switch, which allows for either 2-pickup pair by itself, or all 4 together in parallel.
It doesn't do all possible combinations of 4 pickups, as there is no series option between the two pairs- mo more than two pickups are ever in series together. But it still gives a broad array of possibilities.
Also note the "progressive" slanting of the M1 and M2 pickups,making an "arc" to match the slant of the bridge pup. The idea for that was mine, but the implementation of it was thanks to the late, great ChrisK, who fired up his CAD program and made me a full-sized pickup template for cutting the correct angles for the two middle pickups (The pickguard itself I ordered from Warmoth, using the option to delete the middle pup hole, so I could cut my own two instead).
So, you may wnat to rethink the blend pots, although it's not clear from your post what you want these pots to be doing. And I also don't know how a three-way switch (and, of what type?) is intended to select between the 4 pickups, unless you are just planning for wiring it like a HH guitar.
And, sorry that I had to move your post. Hello and Welcome to G-Nutz2!