The linux subsystem is implemented via Windows kernel modules. "Just sandboxing" has proved to be a pretty hard problem for both kernels, so I'm pretty skeptica

The linux subsystem is implemented via Windows kernel modules. "Just sandboxing" has proved to be a pretty hard problem for both kernels, so I'm pretty skeptical that simply removing /mnt/c would suddenly result in a reasonable secure system. Especially since the WSL code is quite young.