How do you read linux firewall documentation with the first example being old school public->DMZ->private? So your web server got hacked? That means what? Your database is across a single port through the firewall, and ACLs mean that any traffic arriving at the part from the DMZ CIDR can only do the limited set of queries that provide single-person-at-time. SSH from hacked box to database? Got a zero-day for the firewall (because 22 isn't open from there), and a zero-day for sshd (because its keys only). I know this and I'm not one of our hundreds of security people. (And as I'm not the security guy, if any actual security guys want to school me here, please do so!)
Sure, I agree that business peeps will say "Oh that's too expensive I don't care", but lets not pretend that we don't know how to do this.
Be clear, if you are the IT security guy, and you agree to bow down to "business" people (you're a business person) who tell you "No, that's too complicated", then just be clear that you are getting fired when the shit hits the fan.