It's great to hear that my feedback was helpful and that it will help you make the mod perfect.
Personally, I think the multiplier is a great idea, but having both sounds even better. That way, other people can tailor the mod to their own playstyle. You could make it a dropdown option: Vanilla, Multiplier, or Custom Recipe. I'm already a fan of this idea!
Your description of the ICBM is exactly what I had in mind. That way, I can clear entire areas of biters at once, but it would require a significant investment. Or I can use a tactical mini nuke myself, which costs less material, but I have to get into the fight and not just press a button.
What's important is that all the options are configurable for both variants. So if someone wants to use a powerful A-bomb, they can make it so expensive that it's worth using, but it doesn't make other weapon systems obsolete, like the artillery. And then you could just introduce a new remote with a cute little atom symbol, perfect!
I think it's also important to have an option to choose whether the nuclear missile should remain vanilla, be only an ICBM, or have both with their respective options.