Mhwd should also be fine with local packages
Assume I have a very old kernel version I want to keep installed, but I also want to install some whatever driver. If you purged the related kernel module package from official repos, mhwd will abort.
Now, I'm not here to complain about that in itself (even though an "ignore kernel" switch wouldn't be bad..), but mhwd also fails to work even after I successfully manually installed the required module from cache.