I took a closer look at Space is Fake, and as you said it's pretty close to working already so I'm open to building in compatibility between the mods. However, I'd want to do it "properly" with a full compatibility pass rather than just putting in a way to get lava/tungsten and leaving it still half-broken.
Moving the free EM plants and Foundries you get at the start of Fulgora/Vulcanus into the Nauvis starting items and making a stone > lava recipe in the foundry seems like a good place to start, and melting rocks to lava feels like it makes sense.
Also need to change the Celestial drill to not require big mining drill to craft (probably swap it out for some electric motors) and add a way to get Ammoniacal Solution (Water in a Chemical plant? Not the most creative option but good enough). There won't be a way to get Primordial matter, but as far as I can tell that's just an alternative way to get Crushed divine matter which you can get from Celestial matter so that seems fine?
I also notice that trees give a whole mess of seeds and spoilage when they're harvested which could be a real pain given you need to grow many, many trees right from the start of the start of the game, so maybe I need to give the player a few heating towers at the start too.
Anything I'm missing?