Hi Cheese&Apple. Yes, I think you could do that, as the Library format is now common between iPhoto and Aperture. You wouldn't even need to set it up: you could just read the iPhoto Library in Aperture. It's something I was thinking about doing. I haven't done it yet as I find Aperture slightly cumbersome just as a viewer (I tend not to do much editing of my iPhone photos beyond what I do on the phone itself), but as my frustration with iPhoto increases the disadvantages of Aperture seem smaller compared to its advantages.
The one thing you couldn't do if you did it all in Aperture is have only the iPhone photos go to iCloud, at least not automatically. As I understand it, either everything in Aperture goes to iCloud or you have to do it manually, by photo or group of photos. OTOH, if you use iPhoto to import the iPhone photos (even if you only use Aperture to view/edit them) you could set up iPhoto to send eveything to the cloud. You can only have iPhoto or Aperture linked to iCloud, not both.
Cheers.