As Nathaniel noted, the "solution" of placing DLLs in the same directory as extension modules is not a solution. I also think that some people here misunderstand my proposal: I'm not necessarily proposing that these directories are added using an import hook: they could be added on startup through a scan of site-packages.

"However, even if this were implemented we'd still need to write and maintain the __init__.py injection code for the next ~5 years, so probably the thing to do is to implement the __init__.py approach first and wait to see how it shakes out before considering interpreter changes."

Yes, this approach is already implemented in NumPy and SciPy. I'm also implementing it for other packages as well. However, the principal reason that I'm opening this issue is that Ray complained that packages shouldn't be altering the DLL search path: the only other solution that I can see is to make this documented behavior, only on Windows, and only because the Windows developers (and I'm in no way anti-Windows, but I'm just frustrated with this particular issue) decided to place an arbitrary limit on probingPath.

As far as the complaints about rpath: this is a mechanism used by every single manylinux and actually most OSX wheels, and it works perfectly.