Funny, I was in exactly the same position as you about a month ago. I had a pair of AIV Mules in my Les Paul and loved them but wanted something a bit smoother in the neck and a little different in the bridge. I actually wanted a bit more bite in the bridge than what the Mule gave me.
Anyway, Tim suggested an AIV Stormy Monday in the neck and a Riff Raff in the bridge and it is spot on.
The SM is super sweet in the neck, great for clean blues. I really love the low end which is a bit cleaned up in comparison to the Mule, very tight and poppy. That pickups shimmers, almost rings when played. Beautiful.
The Riff Raff may be a little hotter than what you are looking for but I love that combination. :D
Great to hear your thoughts. I would probably like that combo in another guitar, however not in this one. This guitar is really awesome and I love it, but it has tons of attack, lots of sparkle and treble so it doesn't really benefit from pickups that are bright or edgy in the bridge.. Also, I mostly play clean sounds or SLIGHTLY crunchy, just on the edge of breakup.
I love distorted sounds and all that but I just have NO use for them right now as I play pop and pop/rock and my marshall 1974x breaks up pretty early so it has proven to sound best with low output pickups. Everything may have been different if I used a fender amp.
Anyway. I'm waiting on a rewind of my p90's pickups for my les paul custom that Tim is making and when I get them I'll know how it feels to use low output pickups, so it might help me decide on the pickups for the other Les Paul. Perhaps I feel by then that I will need the extra gain in that guitar so that the two guitars will compliment each other better. On the other hand they won't ever sound the same anyway cuz it's p90's in one and humbuckers in the other.