Got rid of the mod, the biters ain't commin back

If you explore into new territory, there will be new biters there. Once there are some new biter nests, they should start spreading again.

I don't know if it's feasible to create some spawners in far away territory when the mod is removed. I can investigate that if the first solution isn't enough, though.

I have a slight problem with that............
https://imgur.com/a/ItYOw6s

Is there a way to save the biter places locations then replace them when you get rid of the mod?

Heh, I do see your problem.

Your idea should work. Just requires a bit of work to figure out how to save spawner locations in the save file etc. I'll investigate

I think it is feasible but wouldn't you need special permissions to create files in the map folder outside the mods folder? idk factorio coding, the most I have done is Java for Minecraft. Another idea is that you can add the biter nests yourself?

I believe this should be sufficient for saving data:

https://lua-api.factorio.com/latest/Global.html

I can just keep track of the most recent 100 or so nests that were destroyed. I still need to figure out if there's a way to run a migration when a mod is deactivated

The plot thickens...

https://forums.factorio.com/viewtopic.php?f=25&t=76693

You could also try using something like the mod Delete Empty Chunks to delete generated chunks, but it would mean you would have to explore your island again.

Weird Suggestion: take an image of the map before the deletion process and save/store it.

Then/If they hit the button to restore previous biters, scan the map image for the red squares that match the size of Spawners.
If you want to get real fancy, add a GUI like the Blueprint editor crossed with the Map image to select what to respawn and stuff.

Analyzing an image of the map isn't really necessary. You can see exactly where the biters are when they delete them. The biggest issue with that in my mind is that the biters would potentially appear in the middle of a base if you built in that direction. I never really came up with a good answer for how to put biters back on the original user's island without dropping biters in the middle of everyone else's stuff.

One of the mods I use (not sure which one) adds a no-build area around Spawners with a radius of about 20 tiles.
Could the opposite be done? With disabling Spawner placement around Player built stuff within a Chunk or 2. (not a perfect fix but they wouldn't spawn inside the bases anymore lol)