I thought you were aiming at finishing replicas and updated versions of the official maps first, but it's nice - and definitely exciting - to see you tackle historical maps.
Can't wait to see the result, and the discussion around them.
You were quite correct - I am still working on finishing off my replicas and updated maps. But Chimpman sent me a PM about starting threads for these maps, which he's working on now. I'm very happy to have them here in the mapping forum, and I will definitely take part in the development here as much as I can. When I finally come to making my own version of these historical maps, I'll use whatever we come up with here plus my own research and ideas. But right now I think Chimpman's map is already looking very promising.
Chimpman wrote:1) The climate zones are different, with the major example being that Nithia becomes a lush temperate zone, and Alfheim a desert.
GAZ5 describes pre-Canolbarth Alfheim as a "forbidding place" of "wind-torn steppes" which "had rarely tasted rain before". It also mentions how the "water-starved steppes plants suddenly changed and adapted overnight." (All quotations from GAZ5, page 8.)
So it seems that the area was steppes and grasslands rather than an actual desert. It also sounds like the surrounding lands are more fertile, since "the surrounding humans were immediately covetous of this newly fertile land" of the Canolbarth Forest. The area of modern Darokin is probably pretty similar to modern times.
2) I think it's also likely that the course of rivers may have changed over 2000 years.
That seems likely, indeed. Good thinking. Perhaps we can come up with some concepts like this that will be useful for all the historical maps.
3) The original Atraughin plateau was destroyed circa 1700 BC. I'm not sure what it should be replaced with, but for now I'm postulating broken/rugged terrain.
You seem to have done a pretty good job. But remember that the original plateau was much smaller. You could probably reduce the range of broken terrain to about half the size.
4) It's roughly 700 years since a devastating explosion was triggered by a group of elves in the Broken Lands. I'm not sure how much damage that would have done to neighboring lands or how long it would take for nature to repair itself, but I've extended the desolation of the Broken Lands in this map.
You extended it, but quite subtly, right? It looks fine to me.
1) Ranak - According to HWR2 Ranak was the capital on the outer world as well as in the hollow world (for a time). Placement is uncertain.
I would want to make it slightly more central, perhaps closer to modern-day Ylaruam. In fact it would be very fitting to have it on the exact same site - perhaps the Immortals wanted another settlement built on top of the scoured ruins of the old city just to make sure it all remained hidden.
There's also the interesting Hollow World Delta Kingdom/South Kingdom split to think about. It does seem like something that originated in the Hollow World, but it might be fitting to split the country east-west into two (competing) regions nonetheless.
More official stuff on Nithia at this time: "The Nithian Empire is at its peak; it features monumental architecture, large urban complexes in the delta region of the River Nithia, conquest of neighbouring states, establishment of more remote colonies, and the development of more sophisticated arts and culture." (Hollow World DM's Sourcebook page 14.)
You're off to a great start here.