Yeah! If you have it up on github or something, would gladly like to take a look at it to see how you did it!
That sounds pretty fun indeed if they can help defend your plants. Would you be able to give them quality based on their nest? Kind of like the bitter nests, but the actual the entity would have more health, speed, etc etc. Even if that isn't an intended feature, what you have so far sounds really cool!
Ha! Glad I am not the only one thinking of this. I had the thought it being like creep from StarCraft 1 and 2, or Creeper World 4, where there is a node that produces this ever growing spread of creep. Pollution causes increase rate of growth, and if provoked by an attack, the spread moves faster towards your base. As evolution continues on, harder creep is created, but little/massive tendrils spawn to act kind of like worms, but are able to shoot at walls and such to poke at you while the creep spreads towards your base to cause contact damage. To add onto it, you could harvest this creep for further tech that helps fight against it or something. Those are my initial thoughts to the idea :p
As for modding, I just started roughly a month ago myself all due to posting a bug on someone else's mod. It kind of inspired me to start making my own from that :p Still have a lot to learn, like making custom spirits for my mods, as I like to do more then just recolor/tint versions of things, lol.