If I ran the Mac division at Apple, I would bring back PowerPC, but not in the way you would expect...
First, the Mac Pro would get a new version, that is actually usable as a Pro computer. It would have a IBM POWER9 CPU, you can upgrade the CPU yourself, with any Sforza POWER9 chip, you can have anywhere from 4 cores/16 threads all the way up to 22 cores/88 threads. Mac Pro would have 8 DIMM slots, each accepting up to 128GB DDR4 ECC sticks. Also, there would be enough PCI-e lanes for any cards you want. It would use a AMD WX 3100 GPU, and a Universal Audio DSP card.
I would commission a team to port the newest MacOS back to Power9, and build a program like Rosetta, but in reverse so that any Intel MacOS program would run 100% seamlessly. And I would bring back universal apps. There would be an 8-port SATA controller, and 8 drive bays, and an optical drive(for quad-layer re-writable blu-ray support), and an additional 5.25" drive bay. Lastly, this would all be in a case that is very similar to the old PowerMac G5 case.
Also, just for Sh*ts and Giggles, I would port the newest MacOS to PowerPC G5, and charge $50 for it.. And it would also have the new Rosetta program...