I believe the best route still is not the post-apocalyptic plan but the remedy of the present. If sustainable agriculture is just widely practiced, scarcity won't be experienced. People from all roots and races, may they come from first world or third world countries should work hand-in-hand to achieve the perfect sustainability.
If we could just set aside our differences and achieve a common goal, then the vault won't be needed. Let us all take good care of our nature as we only have one of it.
I totally agree with you, @luigienius. I think Cary Fowler had different perspective on this and anticipate different strategy. Though what you've said are definitely doable, he just envisioned to build a facility like this if in case (just in case) all existing crops got extinct and destroyed because of global catastrophe.
Thank you, Sir for reading my post.