[@SpookySquid]
I actually really like that idea and gonna start using it 

Edit: Going by a 5/6 star rating system, the two aliens in City K and S were 2 1/2 stars while the alien in City T is a 3 star. These two new threats will be 1 1/2 stars (for the lower heroes, gotta show em some love~) and the other being 3 stars as well