Do you mean as opposed to three or more? That would be less practical, although some fields, like philosophy of mind, certainly have very many competing theories!
I would certainly like there to be more collaborative truth seeking. But, as said above, I don't see it becoming the norm, certainly not in the short term. Tetlock and Mitchell, for instance, deem it "least feasible when most needed". (1)
I agree that convergence would be ideal, but I'm quite pessimistic of how often it could be achieved even if our culture of discourse encouraged it a lot more.
Here, the synthesis would of course ultimately rest on the shoulders of the reader. It would be up to them to assess which of the sides has made the better case for their thesis. The iterative nature of the argument would at least ensure that obvious counterarguments aren't left unanswered, or if they are, the reader would have a better chance of noticing it and could then adjust their beliefs accordingly.
Another benefit from an iterative approach of this sort: the reader would have only one self contained argument to consider from both sides instead of having to wade through possibly a long sequence of rebuttals and rejoinders in which the forest is easily lost for the trees.
I've been toying with an idea of developing two competing theories in parallel in an iterative manner:
This would be different from adversarial collaboration, as it's commonly understood, in that both sides would work on their own arguments instead of trying to agree on a common summary (which is very hard!).
It's worth emphasising that the idea is not to correspond with the opponent. Instead, one would keep updating one's thesis to meet the challenges presented by the competing thesis so that it remains coherent and
Survey completed!
No doubt it would be hard to get people to do what's depicted in the post. The conjecture is that in many important instances it would be considerably less hard than collaborative truth seeking. But it's just that: a conjecture. Still, I would think it prudent to explore many different avenues here given how unfruitful debates so often are and how much so often is at stake.