The Old Computer Challenge (and various similar things) just make(s) me wish we had properly cared about secure Free Software OSes back then.

Isolation the likes of which Qubes achieves really /doesn't/ require memory-heavy VMs if you start with the right primitives and build the OS from the ground up.

Some capability-security OS written in some language that easily reifies this aspect (Language-Based Security simplifies a lot of things), like Common Lisp, could achieve similar isolation in ephemeral "worlds" with a fraction of the compute resources.

>512MB~1GB to isolate an environment from the rest of the machine? How about ~1MB or less instead?