One thing I’d love to do is a Smalltalk implementation where every message is processed in a separate thread. Could be a nice educational tool, as well as a great excuse to push workstations with hundreds of cores.
Another idea is this: in the ST-80 VM, the only "real" thing at the OS level is SmallInteger. Everything else is a true object reference. One could imagine expanding the base integer size to 128 bits and having all references also described at that size. The reason to do this would be that IPv6 uses 128-bit addresses, and therefore we could bind object references to IP addresses at a lower level.
That aside, the fact that the Opensmalltalk VM is made inside of Smalltalk means that -- in theory -- a team could iterate to that point using the environment itself.
Snarkiness aside, that would be interesting. Not just as an educational tool, but it might be useful in the same way as erlang is (large, fault-tolerant, massively parallel systems). But with OOP instead of FP (Elixir attempts to be the "friendly"/more conventional version of erlang, but it is still very much a functional language).