For more demanding emulation I thought it might be a neat idea if
DOSBox could use the KVM virtualization driver in Linux (and eventually,
equivalent interfaces in other OSes) which could then be selectable
by setting core=vmx.

To explain: Almost all modern CPUs have virtualization extensions
built in (Intel VMX and AMD AMD-V). In cases where a DOS or Windows
game is very demanding, why not code DOSBox to allow using those
virtualization extensions? If done right, the game could run at
almost native speed of the processor. It would also open the
possibility of running more modern OSes under DOSBox (ones that
would normally run too slow in the full and dynamic cores).