Hi R.R.
I would advise against going Riff Raff Neck / Stormy Monday bridge, as the 'magic' combination is usually the other way round, - a nice biting Riff Raff at the bridge, contrasted by a sweet yet clear Stormy at the neck. I also found that an Alnico II Stormy could get a bit 'soft' or 'wooly' in the bass when in a largely mahoghany guitar. Even as a matched set, I eventually asked Tim to fit Alnico IV magnets, and whilst I lost a little sweetness - the E.Q. balanced out beautifully.
My two ( vintage ) choices for you would be :
1 ) get a matched pair of Alnico IV Mules.
2) Ask Tim to build you the bridge Riff Raff to complete the set.
I put the Mules at number 1 though, as you like to play a much wider range of music, and they certainly 'fit the bill' in doing that. The Mules have a slight mid - range 'hump' too - so if you have been used to the fatter sounds of a P90, the Mules would be more familiar than perhaps the 70s Rock excellence of the Riff Raffs, or the 80s majesty of the Cold Sweats.
Of course , if your tastes run into heavier and tighter territory too, having the Cold Sweat set completed would also be a permissible 3rd choice.
The nice thing about B.K.P, is that there is no 'bad' choice, only differing degrees of 'appropriate' choices.
Perhaps consider deeper, ( or let us know ) - what artists and tastes you are most likely to be playing like / getting excited by ?
Welcome aboard ! :D