I've been watching these attempts closely. I'm encouraged that you updated to version 18 quickly. We want to implement this on our server cluster. The other surface mods have been rather buggy, and this one was for a while -- still is, right? Do you think you'll be maintaining this for a while? I can and will help if you're in it for the long-haul. Using something like this is a long-term goal of ours. Our long-term goals involve also providing different geographical characters to each surface, but I think getting the framework right first is important -- from your other comments it sounds like you have the same idea, although I would argue that pollution transfer should probably be part of the framework. I don't think it will be hard, but should definitely be a v2 feature if you're still working out some of the basics.

Hi, I've been working on my own version of this mod, because I don't really like the way this mod is currently implemented. It's not really flexible and focusses only on a specific type of surfaces.

I've made some progress a couple of months ago and currently you can teleport to a cave surface (which is by my knowledge the first mod to implement caves with the actual built-in map generator).

You can follow both projects here, in case you're interested:
https://gitlab.com/Danacus/factorio-surfaces
https://gitlab.com/Danacus/surfaces-caves

You can try them out if you want to, but currently the only way to teleport between surfaces is by using the surface_down and surface_up commands in game. I should also mention that these mods depend on the Factorio Standard Library mod.

I want to continue working on this mod, but unfortunately I haven't been able to find a lot of time, mainly due to university.

Maybe I'll try to implement some more basic features in the next couple of days, while I've still got time.