Very few people are actually answering the OP, he is asking what roadblocks beyond disc encryption would exist.
Not in any particular order:
1. (You already mentioned) Memory bandwidth
2. PS4 has a unified memory architecture; PCs don't.
3. PS4 has hardware support for cache coherence between CPU and GPU. PCs don't.
4. PS4 will allow lower-level access to the GPU than will be available to emulators on PC.
5. PS4 will expose architectural details of the GPU to the developer. Even if the emulator had the same direct access, you couldn't exploit it in the same way, because the emulator has to run on PCs with a variety of GPUs.
There are more, but those are the first things that popped into my head.