Yes and no. They're CPU bottlenecked but not due to the lack of raw performance, but due to the fact that those custom architectures had some IP blocks that are

Yes and no. They're CPU bottlenecked but not due to the lack of raw performance, but due to the fact that those custom architectures had some IP blocks that are so radically different that what you can find on ARM and X86, that can't be easily emulated in SW no matter how much raw CPU power you throw at it. This is where you need to use FPGAs, but getting a 1:1 soft-core clean room reverse engineered clone of a PS3 Sony Cell processor would be a monumental effort we're unlikely to see anytime soon. It would probably be easier to reverse engineer the games themselves and use hooks to replace the API calls that use the custom IP blocks with standard Vulkan API calls that achieve the same functionality for example.