The idea of it being invasive species (UBs invade Alola) doesn't mean every UB is based on an invasive species from our world.
still it sounds fun so I'm just gonna spitball:
1. Kartana is certainly based on origami.
While it means "folding paper", the word gami can also be punned into meaning "God". Items becoming dieties or lesser demons in Japanese culture isn't uncommon. Maybe it signifies the man's might create a powerful enough weapon that can be revered, and it has the potential to wipe all of us out?
2. Speaking of Japanese culture, Blacephalon looks like possessed Japanese Tanabata lanterns that are hung during, well, Tanabata. Possession = Ghost, lanterns = Fire, seems to make sense doesn't it?