What do you do for: - Route-maps. - Prefix-lists. - Access-lists.
Those fall under "configure the router"... Yes, things one does that use prefixes are going to have to be reconfigured using prefixes.
- Firewall configs.
A firewall is either an application gateway or a router depending on what it does; it at minimum receives packets and forwards them, and may translate them in some sense. "configure the router..."
- Customers that are stupid enough...
Someone else's stupidity is not my problem.
- Suppliers that have configured your systems in their hosts.allow.
hosts.allow, last I checked, uses names. But nonetheless, this is (ahem) not the world's most secure mechanism for much of anything (ahem).