Inasmuch as "multi planetary" means multiple _self supporting_ planetary settlements (and otherwise, what's the point?), that seems to be an entirely unrealistic goal for the foreseeable future, so, by definition, there cannot really be a "critical path" to such a goal.

What he has is a plausible path to shipping canned apes for a brief sojourn to a far away locale fairly hostile to long term habitation. If that's what he wants, fine, but there's no reason the regular legal process needs to be waived for that.

The important part of that end is a much more economical tech for putting mass into orbit. I'd argue that is currently the single most effective thing that we can do toward becoming multiplanetary. Yes it still leaves a very long road ahead, but it's a bridge across an otherwise impassible chasm. A related Heinlein/Pournelle exchange:

  Unfortunately, in Blowups Happen a capability for orbiting large payloads had been developed. "Aha," I said. "I see your problem. If you can get a ship into orbit, you're halfway to the moon."
  "No," Bob said. "If you can get your ship into orbit, you're halfway to anywhere."
  He was very nearly right.