I think the simplest way to make conda/pip play well together would be for conda to add first-class support for the upstream python packaging formats – wheels, .dist-info directories, etc. Then conda could see a complete picture of everything that’s installed, whether from conda packages or wheels, handle conflicts between them, etc.
This seems a lot easier than pip growing to support conda, because pip is responsible for supporting all python environments – venv, distro, whatever – while conda is free to specialize. Also the python packaging formats are much better documented than the conda equivalents.
And if we had a single package manager that was clever enough to understand mixed conda/wheel environments, then we could potentially define new wheel targets like “condalinux” or similar, that can be uploaded to pypi alongside more general wheels like manylinux, and can declare dependencies on a mix of conda and wheel packages.
But I’ve pitched this to the conda folks every so often for years now and they’ve never followed up, so 
idk maybe mambo would be interested?