I am surprised that using transfiguration and defeating Voldemort played such a large role in the solution.
I thought that it was much more likely that the solution would be to lose in some way, but to lose in a way that maintained hope / constrained Voldemort's actions to not be evil, and then to continue to work towards a better situation once out of immediate danger.

I also thought that the Vow that Harry had made would be the biggest key to the solution. After all, transfiguring carbon nanotubes and antimatter were things that Harry could have achieved earlier to defeat Voldemort, prior to the situation having gotten truly terrible. (He couldve done what he did to stun and obliviate Voldemort this during the entire forbidden corridor storyline). Therefore, it made sense to me that the new addition of the Vow would be critical to the solution, not just something throw in to stall for time.

Anyways, I am glad that the community collectively came up with all of the elements of the final solution as it was written.