What will happen if both proposal 1273 and 1623 both pass?
Even though the “additions from comments” section in this discussion, and the implied aspect of the discussion of the formal proposal (since it implied that this could save the current system), the proposal itself does not reference back to the discussion, and does not explicitly state that it would stop the fork from happening. It could meet that portion of the goal of the proposal (if I understand the proposal discussion correctly - if not, then disregard this comment) if TerraForm Labs decided to retract 1623 if this proposal passes first, or if 1623 fails with “No with veto” and TerraForm Labs decided to give the current Terra ecosystem another chance. But, if they both pass, TerraForm Labs could implement 1273 on the current chain, and continue with the fork (at least the way 1273 is written).
Unless you have a commitment, or an indication, that TerraForm Labs will see this proposal as intending to prevent another ecosystem from being created from a fork (or you are intending to work with TerraForm Labs to see if they may turn over the current ecosystem), then it seems like you may need to pare this proposal with another proposal that specifically attempts to preserve the Terra infrastructure and would not allow for forking. That complimentary proposal would need to pass in tandem with 1623 - both having the opposite effects in regards to a fork (with the second passing at the same time or a little after 1623). Or, again, to determine somehow from TerraForm Labs what their intent will be if 1623 does not pass and 1273 does (will it pursue another proposal to fork, or will it see 1273’s heart being that the proposal was attempting to save the current Terra ecosystem).
I do not say this for any other reason than as I read your comment it hit me that I probably should point out that observation (it had not occurred to me - I was working so hard on the proposal that I was working with).
I also do not say that to disparage this proposal (although I have mentioned my concerns with it to @HelloThere ), but I think that as you push forward that you consider this in case your proposal does pass (since it is pretty close), that you begin to move to the next stage of thinking so that it does not pass and then not end up providing you with what you all worked so hard for and thought would happen through this proposal alone (the way it is written in the proposal).
If you are not able to get a commitment form TerraForm Labs, then there are a number of proposals out there that explicitly state in their proposals that it should not fork, maybe one of these could be a compliment to this proposal (unless I have misunderstood and this proposal is considered by this discussion community to include either a fork or no fork option as its intent). Here is a list of current proposals (in addition to those that are whitelisted):
I truly hope that helps a little bit - the community that has mobilized around this proposal has been an inspiration to see how hard you are working.