I don't think the destruction of habitats and the decline in the number of endangered species is unique to Mexico. This type of habitat destruction is occurring all over the world and many species, not just axolotls, are becoming endangered or closer to extinction as a result. Therefore, I don't think that taking the responsibility away from a community would solve any issues. I think it is better to work with the community. Education and awareness is key and teaching future generations on the importance of looking after the environment and conservation of species, particularly those vulnerable to extinction.
I would expect that an axolotl sanctuary would have to be some distance from Mexico to prevent the destruction of the new habitat. However I think it is important that it is as close as possible to their native habitat. As already mentioned, it would have to be well thought out and planned by experts in the field.