I don't think it's a question of styles clashing - it's up to you what the pickups do in your guitar. I personally prefer "similarity" in the pickups and have different guitars for different jobs. But others prefer different pickups in the same guitar for different jobs.
But you might have issues with balancing output from different pups in a combination maybe? I don't know though, I've never mixed & matched across sets... and I've only got one set of strat BKPs so haven't got anything to compare against.
It does sound like you're going through what all of us do, especially on a first set, "I want to get it just right..." :roll:
The way I personally look at pickup choices is this - work out what ballpark I want to play in most on that guitar, choose the pups for that ballpark and "compromise" on the other sounds.
I've since found that this isn't too bad a rule of thumb for me - all the BKPs I've tried are actually more versatile than I was expecting. I needn't have agonised as much as I did over choosing ITs, for example...
I'd say, unless you want to go down the mix-and-match route (someone else will need to help there :D) you need to look at the range of styles you want to cover. Which is more important to you, the blues end of the range, or the metal end? If you said blues, then certainly the vintage hot (ITs, and I understand Slowhands as well) can cope enough with early metal stuff to keep you happy - happier than with what you're using at the moment. I suspect even Mother's Milks will do it if a more classic "vintage" tone is important as well.
Hope that helps - don't feel like I've explained it too well! It sounds to me like maybe another chat to Tim might help? I've not had to ask him any questions so far, but I understand he's very patient with us all :D (and you could use up the questions I haven't asked!! :lol:)