haai Laegwen, I think the prospect of a card board box under a bridge is what keeps cookies as a hobby for many people!
In the latest comment on "https://cookieconnection.juliausher.com/topic/fondant-on-cookies" fondant is mentioned as a base for royal icing details. It could save you thetime for icing the base layer, but probably still cost you in colouring the fondant. At least there are machines for rolling it out!
I really hope you find a solution.