I’m not sure that any of the proposed solutions are even close to attaining “silver bullet status” given that almost all of the CUDA software in question is (a) large and (b) needs to support a wide variety of GPUs if you want it to be broadly applicable and not force the user into navigating the GPU version namespace manually and/or suffer long PTX JIT times at startup, assuming that PTX is even an option for all of the GPU kernels you want to publish. The price of hiding such details is large wheels - it’s like a speed of light constant.
I would propose that one solution might be wildcard redirects for very specific vetted vendors. This is to say that rather than doing per-file redirects, which caused the QoS problems that PEP-470 addressed, PyPI just accepts that certain families of packages which are identified as part of a pre-agreed namespace (for example: ^cuda-.|^nvidia-.) do a bulk redirect to the vendor in question, that obviously being Nvidia in my example.
The “vetting” part would also probably involve agreeing to certain QoS obligations. Files covered under a registered wildcard wouldn’t be removed before years, would never be updated in place, would be made available with SLAs on latency and average global bandwidth, etc etc. If the agreement also specified “trust but verify”, it would also be easy enough to expose certain CDN statistics or have bots randomly download targeted files from various parts of the world and report in on whether the the external provider was any worse than the PSF’s designated CDN. If an external vendor started failing to meet their obligations, they would be under threat of losing their wildcard redirect.
TL;DR: I am suggesting that the blast radius of redirection be limited to a small handful of large entities who can pay their CDN bills at scale and meet the overall QoS needs of PyPI while providing large file support.
I could also suggest more radical solutions like IPFS being adopted as a global data store for PyPI and allow this to be sharded across the internet as a whole, but now we’re departing the realm of science and getting more into science fiction.