I understand why its easy, but on Fedora Atomic I even have all the userspace drivers for intel, amd, nvidia and maybe more, even though I clearly just use intel...
The problem is not caused by mono kernel. Just because AMDGPU driver was developed in mono style. i.e. they include the code of all generations in one driver. In monolithic kernel, the developer can develop drivers with "micro" style. e.g. Intel's GPU driver doesn't use mono style, they created a new driver when they changed GPU hardware architecture.
Monolithic kernel is a concept about address space. If all parts of a kernel are running in the same address space, this is a monolithic kernel, otherwise it's a micro kernel.
This problem is about how to split parts, but not how to place parts in memory.
I believe the advantage is that old drivers still work as they are all in the kernel. With them sharing much code it's not even that big of a disk space issue. Edit: A more dynamic approach would be great though, especially with this size issue popping up.
In a way it's great that I'm able to replace any part of my system and it just works without me having to make sure the old GPU driver doesn't leave some traces behind–altough while writing this the latter part shouldn't be an issue with Windows auto download and installation of drivers.