Hi JD,
This probably won't be a surprise to you, but setting password-never-expires is not a recommended security best practice. If you deploy Azure AD Password Protection in your AD forest, it's probably ok to increase MaxPasswordAge by some factor - but not password-never-expires.
Going back to your main question:
>>So having differing policies that can be applied to a subset of users would be of benefit.
Setting password-never-expires seems orthogonal to deploying Azure AD Password Protection. Regardless of whether or not a password will expire or not, it is still a good idea to try to make sure that that password is not easily guessable.
If the concern here is that those users who do NOT have password-never-expires may be "upset" by being forced to select stronger passwords, well I would say that for most customers this is considered a relatively minor cost that is easily accepted given the larger security benefits. If those users are highly privileged such as Domain\Enterprise Admins, then this is even more true.
Jay