One could get the specializer to produce a single-instruction sequence without pipeline overlap. That could be QUEMU emulated, but we have a sim already. The other argument for QUEMU is that it can produce translations that are close to native performance on an alien architecture, saving the cost/effort of a port/retarget. But applied to the Mill that would give close to the performance of a single-instruction sequence with no parallelism, or truly awful in other words.
No doubt someone will someday try to extend QUEMU itself to be able to handle Mill-like ISAs. But not us today on our very limited nickels.