The Valar announce that they've done as much as they can in Singularity (they can't bring back peoples' babies in that critical period either, but they can get them earlier versions) and are setting up portals between there and Sanity as soon as they are confident they've cleaned up the plague. A bunch of Elf architects have this wild idea for a fivedimensional city where alternating intersections are interdimensional portals between various Valinors and they get eagerly to setting it up.
He will try to help with the summoning demand problem! By taking summonses, that is.
And back to Milliways he goes. "Next concordance is Fairyland and coming up, right? If we can get something from Limbo out then the flat Arda Valar can portal in..."
"How recently from Fairyland would it have to be, Hell has some indestructible curiosities from before trains were invented... they'd be unpopular to take but not hard to look at."
"What would?" asks Karen, heading in to collect breakfast from Bar. "...Hi, Minor."
" - hi. How recently from a world something needs to be for the Valar to portal to it. So we can go to Limbo."
Okay. He leaves Ambela a note asking how recently of a place the Valar need a thing to be.
Well, there is a Limbo imported harp known to be in such and such a place if they want to go look at it.
There's a Fairyland concordance soon but they will need to go alongside a very fast train designed to take up all of the space in the concordance.
They can be immaterial, that should not interfere with very fast train. Also that's an impressive work of engineering on the Limboites side to have a concordance-length of fast-moving train's worth of tracks, how did they build them?
The daeva worlds ferried them materials during pre-train concordances.
"Summoning shortage is a real problem. The set of my fathers who are working on that think they might have an angle on non-Milliways interworld transit that doesn't require access to both worlds already, but we can't do anything for those worlds once we find them, not at a rate even vaguely resembling the rate we'd need. And there are another couple Ardas coming up on the parole of Melkor to intervene in."
"At least Ardas at that age don't have humans and aren't so urgently in need of summoning."