Updates on this guitar.
1. After a setup and fret level, I still had "sitar effect". Turned out the nut was low, and so I shimmed it myself to make it right. Lesson learned: professional guitar techs might do a "setup" without checking it out. Learn to do it yourself!
2. Adjusted the bridge saddles with the right number of shims, and most importantly, removed the stock shim that changes it to a 10" radius. Feels much better now.
3. Electronics overhaul. While I did achieve exactly what I set out to do - vintage Strat sounds with a humbucker bridge tone - it turned out that what wasn't what I wanted. I have a vintage-sounding Strat already, so I decided to beef this guitar up a bit instead. Got a Cool Rails neck pickup and put a Vintage Hot Stack Plus in the middle. At this point the middle pickup was half the volume of the other two, which didn't work at all. So I replaced that middle pickup with a Vintage Rails. The VR comes with 4-conductor wire and is intended to be wired in parallel, but I wired it in series instead for extra volume. It still more or less sounds like a vintage strat middle pickup, but much louder and a little bit more hot.
With all three pickups now humbuckers wired in series, there's no need for a clever switching system - I replaced it all with the completely standard Strat 5-way, one pickup wired to each of the contacts and no splitting at all.
It sounds really great through distortion now, and I think the looks are a bit more interesting too:
Video to follow in the next few days.