Allow route subs and customer specific sub list to work together

We just started to use route sub lists and then learned that if a customer has a customer specific sub list and a route sub that it only looks at the route list. Can you add a column in the sub list to determine if it a route sub or customer list? Then hopefully the logic could be worked to look at route sub list, then customer sub list and last line item sub list. I would say if it finds it on any list, it stops and executes that command.

Otherwise we are really in a bind when trying to use route subs.