I actually wonder how much "overhead" a VM actually has. i.e. a linux kernel that doesn't do anything (say perhaps just boots to an init that mounts proc and every n seconds read in/prints out /proc/meminfo) how much memory would the kernel actually be using?
So if processes in gvisor map to processes on the underlying kernel, I'd agree it gives one a better ability to introspect (at least in an easy manner).
It gives me an idea that I'd think would be interesting (I think this has been done, but it escapes me where), to have a tool that is external to the VM (runs on the hypervisor host) that essentially has "read only" access to the kernel running in the VM to provide visibility into what's running on the machine without an agent running within the VM itself. i.e. something that knows where the processes list is, and can walk it to enumerate what's running on the system.
I can imagine the difficulties in implementing such a thing (especially on a multi cpu VM), where even if you could snapshot the kernel memory state efficiently, it be difficult to do it in a manner that provided a "safe/consistent" view. It might be interesting if the kernel itself could make a hypercall into the hypervisor at points of consistency (say when finished making an update and about to unlock the resource) to tell the tool when the data can be collected.