While we're sorta kinda on the subject of ERB, I'm curious which of his works you plan on incorporating?
There are a number of 'em that reference each other in some way (Tarzan visit's Pellucidar, which trip is mentioned in the first Amtor book; while technology from the Pellucidar series is used to contact Barsoom, which is mentioned in The Moon Maid), and there are "cosmological" similarities between others (Va-Nah is the Moon's interior just as Pellucidar is Earth's; astral projection serves to get John Carter and Ulysses Paxton to Barsoom, "Loto-El-Ho-Ganja" to Amtor, and "Tangor" to Poloda). OTOH, the Barsoom books have WWI ending as IOTL, while The Moon Maid has it lasting 'til 1967, and I believe Beyond Thirty had it last even longer.
Well, I want to do Earth+Pellucidar, Venus/Amtor, the Moon+Va-Nah, Barsoom/Mars and something on the Jupiter of the skeleton men, so I'll have to work around the inconsistencies. I plan to have things on Earth fairly similar to OTL up until the 1930s, by which time alternate physics, the opening up of the remaining Lost Kingdoms of Africa, and the increasingly wide spread knowledge of a hollow earth are going to seriously impact things no matter how many butterflies one stomps on...
Bruce