Could we have a map setting to start with a single spiderbot boi? I can obviously insert one with a command or the editor, but that nukes achievements which is a shame.

I wrote a mini mod that does this:

https://mods.factorio.com/mod/spiderbots-quickstart

Let me know if it becomes obsolete if you fold this into the main mod.

I like the mod you made! Since I've added a technology unlock for the spiderbots (mine a fish), you might want to consider having the quickstart mod unlock the technology when it distributes the spiderbots.
If you still want me to add it as a startup option to this mod, let me know - I'm open to it even though I think you did a great job with the one you made!

Thanks @asher_sky -- I don't think my mod touches the tech tree. It would technically be possible to have the mod wait for the tech event and at that point inject the starting bots into the inventory. But I'm not sure if that adds anything. If you want to simply absorb my mod into yours, please do so and I can mark mine as retired. Feel free to loot the code. Otherwise, I'll leave it in a semi-abandoned, semi-maintained state like my other small mods.