Honestly if communication was possible between worlds, then it is very likely then travel would be as well. Under that premise then it might just be a matter of migrating everyone from one world to the Source and find a way to siphon off that aether from that shard.

But with that said there are still issues considering that it would entail displacing an entire world's population, a migrant crisis that might make RL ones look like child's play and then there's the possibly that any attempt at rejoining a land, depopulated or otherwise, would still be a disaster worthy of the title of calamity, and thus merely lowering the risk and means of dying form "guaranteed cessation of existence" to "snowball's chance in the seven hells that most of the now doubled population survives".

Oh and going with the disembodied soul form of travel like the Scions did has further complications (namely that their life still depends on their body on the Source still be alive) and is more a unexpected astral projection if anything. Ardbert and his group' takes on it required suicide so that falls under the issues inherent with the original proposed solution of the exercise and also the issue of Self-sacrifice that no one would agree too unless their world was doomed anyway (the exact scenario that is the reason Ardbert, Lamitt, Raena-Rae, Nylebert and Branden made their sacrifice and also the one that apparently necessitated Zodiark's conception).