I'm glad Brad is thinking on these terms. It bodes very well for the fun-ness factor. It seems to me a core choice is one that sets the tone for at least the next few minutes of the game, if not longer. Air vs. land would be such a choice. T1 vs. T2 would be. Orbital vs unit spam vs defensive buildings another. 

I'm having some trouble with factory vs. expand as a core choice in 0.71. If you choose to build the factory right away, you forfeit your ability to gain a region before the neutrals spawn. This path puts your unit production about 15 seconds ahead of the expand choice, but not really because you have to send units to grab that region eventually. As such, it is never better to build the factory first, so it's not really a choice.

There IS a choice for the expand option though: metal or radioactives? The former may allow you to sustain spamming T1 units and weak defenses for longer, whereas the latter would give you earlier access to more quanta and advanced units. This choice could be made starker by giving the player a one-time per region bump in the associated resource the instant they capture a region (say 50 for radioactives, 100 for metal). This would also make the subsequent order of expansion choices more impactful, and would help with some of the early game economy stall problems.

It seems unlikely to make all current paths viable. Building a dread factory the instant you have access to radioactivess for example. I can see it being possible to eliminate non-viable dead ends by making the dead end paths unobtainable until your economy can handle it. But then the game is putting restrictions on build orders so there are only a few paths. This means you are still following optimal build orders; the game is just funneling you into them. There would be reduced potential for novel builds, or builds unique to particular maps or team arrangements. Is there some other way to retain build variety while still eliminating newbie traps?

Surely what is viable or not depends on the map. 15 seconds here or there is not going to lose you the game on a huge map. Also if you don't know the map and you have terrain obscured you may play differently too. Under those conditions I get a Pan out much earlier so I can see and get a feel for things. (I really hope random map maker a-la Civ makes it into the game at some point as exploring unknown maps in-game are fun and add to the experience, for us casual players at least)

I do hope there is not just one best opening strategy on the smaller maps for obvious reasons.