Assign Order Status by Shipping Method?

This is my situation. I offer free shipping but all free shipping orders are held for two business days, as I assist those who paid for rush shipping first. I crated a brand new order status called “on hold”, talking about how their order is being held because they paid for free shipping. When a new order comes in and realize the customer paid free shipping, I have to go in and physically change their status to “on hold”. This would not be an issue if it wasn’t for the fact that once they place an order, even with free shipping, they get an “order processed” email explaining that their order has been placed successfully. To later send them a second email, saying, “oh, wait, actually it’s being held” starts a stir!!!

Is there anyway, in admin, for me to say “if a customer requests this SHIPPING OPTION, to mark their order THIS STATUS?”. I know sometimes when I card fails, it creates the card failed status. I also see statuses are marked with letters. Can I apply those somewhere?