Let's see...
Mac Mini: Starting model should be as powerful as the entry rMBP, should be upgradable, have 8GB RAM standard, have Intel Iris, and since it's a low-end computer, maybe we could forgive the hard drive, as long as it's a 7200RPM. Higher-entry should offer i7 Quad-Core as base, but with SSD or at least a Fusion drive.
iMac: 27" should have NVIDIA graphics, 21.5" needs to be slightly less powerful than the 27", but should still have high-end specs (that includes an SSD/Fusion Drive and discrete graphics!) and 4K standard (and please, 2160p, not DCI 4K)
Mac Pro: NVIDIA graphics, 512GB SSD, 16GB RAM standard, and all that other stuff that needs upgrades.
MacBook: Second USB-C port, very small (adapter, not wire) USB-C to USB-A included in the box, and 14" model available as well. Also, nerf the MacBook Air.
MacBook Pro: Redesign with upgradable RAM, USB-C, all that good stuff. Make the border of the device thicker, in favour of making the "base" thinner (which will result in the same total thickness, but with more place for ports, because I WANT THAT ETHERNET). Bring back the 17" model as well.
iPad: Only one model of each size, iPad Mini stays the same, iPad Pro 9.7" should be called iPad Air 3, iPad Pro 12" should be called iPad Plus. No protruding camera, rotation switch back. Prices more consistent.
iPhone: Explaining everything I want with the iPhone would take me an hour.
These are super-unrealistic, I know, but hey, a man can only dream.