Providing the headers by default
I think it will be a good idea that when you install a kernel, the headers package is also installed by default. It saves trouble.
For example the package "deepin-anything-dkms" provides the file "/usr/lib/modules-load.d/anything.conf", which invoques "vfs_module", which requires the headers to work.
But since Manjaro has a headers package for each kernel, any other package in Arch that assumes a single headers package will find trouble.
That's usually the case with virtualization solutions. If they are not the most frequent ones they frequently fail to launch properly.