>Agree with your hypervisor/architecture point but I suppose there has to be some broad architectural choice made.

There's a risk that the VM platform decision could date and, ultimately, render useless an experiment sandbox.

However, two points. Firstly, any attempt to wholly encapsulate an experiment will be susceptible to problems concerning the technology choices made. By choosing the abstraction at a VM level, you're more likely to get a better number of years out of your choice than picking specific programming languages (which I contend would fail to gain adoption as researchers wouldn't change their obscure toolkit if they felt it was the right one for their research).

Secondly, even a VM for an obsolete architecture is better than what we have today - the original paper and perhaps an email address for the lead author.