well, if you were asking hss in general, i would've told you: Two forum singles and a p-rails. It's what's going to be in my strat come christmas, and i'm telling you, it simply won't get more versatile than a strat that can get strat, telecaster, les paul & les paul junior sounds. Realistically, between those 4 you've got just about all the bases covered.
5. P-90, single coil - my two favorites for cleans
4. P-90s in parallel, single coils in parallel, bringing us to quack city and the second most used position on my 5-way
3. Middle position - a dedicated telecaster sound neck + split coil bridge
2. Bridge split + middle
1. Bridge series (switchable to parallel)
so i'm going to need two push-pulls - one to tap the singles in the neck and middle, and one to switch the bridge from series to parallel. I'm going to use a blender/split pot so i can get just the bridge p-90 or the single coil without having to use them with other pickups.
So that's what you should do. On the one hand, if you look at the output of the guitar when it isn't tapped:
15k neck
16k middle
18k bridge
vs. Tapped
7.5k neck
7.8k middle
8k rail coil, 10k bridge p-90
it'll be the best of all worlds, when i get it together it should be righteous indeed.