I might be in the minority for this use case given the mod title, but I was using this mod to simplify the vanilla planet logistics and not avoid space entirely.

I have a save with a lot of modded planets, some of which are prevented from generating due to missing terrain generation features. For example, the Shattered Planet mod relies on a terrain generator from Vulcanus and Maraxis relies on one from Fulgora.

Is there any possibility of not deleting the vanilla terrain generation features?

Thanks for the mod I am thoroughly enjoying the all-Nauvis vanilla experience.

This simply fixes a few minor things for the mod Everything on Nauvis, I am not the author of the mod. Unfortunately he has been away for a while now.
To resolve these issues, the original mod would need to be changed. There are forks of Everything on Nauvis for Factorio 2.1, they might be able to make the required changes.

Thanks for the reply I will follow up on one of the forks.

You could try my fork but it adds Fulgora back. There are startup options that can significantly change the setup and it should be much more compatible with other planet mods.

For now I just removed the lines that deleted the autoplace controls in remove-planets.lua. I am not sure what functionality they have but everything seems to still be functional without them and now Maraxsis and the Shattered Planet are fixed.