I don't have any experience with the dog-eared Franzs on the X-175, but I can say that the soapbar style installed in the M-75 Aristocrat (and presumably some of the NS solidbodies) cannot accept a P-90 as a drop-in replacement. There are definately some P-90's that will fit under the Franz cover, but it would require some work; use some parts from the Franz and some from the P-90, possibly modified a little. It's possible that it would be easier with the dog-eared version, but still, the Franz mounts differently than the P-90, so it won't be a simple swap.
In the end, the NS Franz repro's are a good start. If you're looking for something different - and can articulate what that is - then the best alternative might be to send the pickups you have to MJ at Seymour Duncan and have her rewind them for you, possibly with a magnet swap. But, again, it's important that you can tell her what you want.
My last word on NS Franzs: they're bright with a very sharp peak in the high end. If you turn down the volume and tone controls on your guitar it will damp the peak but still let through a lot of sparkle. If you're the kind of person that leaves the knobs up full as a matter of habit, you might try experimenting a little.