I was hoping that would be prize for temples; heros arrive at assigned town 10% faster. Think its better than cheaper level ups imo. I like the faster idea, but the immediate for gold could almost be used to snipe; maybe there would be a cool down period; can only gold (instant hero arrive) once per town per 24 hours. Or cant assign within 5 min of an arriving attack like the barracks purchase. I could see a golder stopping a revolt by instant zathura, then instant perseus, then instant leo, then instant urph, hector, pelops, etc.
I like the idea in general but would need some work.