How we can be adapted Amalgam Universe concept to Original Works

May I ask everyone here about concept of Amalgam Universe which is basically universe where Character from two different universe are merge but I want to adapted it to Public Domain & Open Source Character from Charlton Comic,Fawcett Comic to Mythological character,Historical Character & Fictional Character

What will the universe be like?

such as Wizard of Oz & Alice in Wonderland Amalgam Character an the world

Surely it would work in pretty much the same way as any other such amalgam? If you know of other examples of such, whether they use source-works that are under copyright or not, you might look to those for inspiration.

As to how the universe would work, that would depend heavily on what source works you merge, and how you do so, I would say. To a large degree the "rules" of the merging would be up to you, I imagine.