I think aftermarket parts availability, Like sights, holsters, action work must be considered. I think that rules out the Ruger. An aftermarket part to make the trigger good rules out the shield. The XD's don't have a reputation for durability and the one I had with a Springfield custom shop trigger reminds me of the P30 trigger which does not make me think good trigger at all. The PPS is not that available and lacks support from the parent company. I have a Kahr P9 and although I love it for concealment the trigger sucks. It also lacks modern refinements such as adjustable backstraps.
I don't think the pistol I am describing has been made yet. These comments are either based from personal experience, P30 XD Kahr, or from what I have read online Ruger Shield PPS. YMMV
I'm not thinking tiny pistol. I am thinking full grip size but slender. As many 9mm bullets as can be crammed into it. I would definitely support a thicker staggered column grip as long as the frame and slide were not thick. I'm not sure how they would do accessories such as laser and light but if Crimson trace were brought on board I'm sure it could be worked out.