This would be better done with a VPN than simply allowing external access to your printers.

That works until you're sitting behind another NAT that uses the same internal IP range as the one you connect to over VPN - which is very likely since everyone uses 192.168.0.0/24.

Assuming the VPN server doesn't just allocate from a pool of public IPs owned by the organisation you're connecting into (the scenario I had in mind here) then yes this is an issue.

I'd guess that the NAT+NAT problem is more common than the enterprise variant, since very few companies other than enterprises have more than a few IPs.

I'd wager it's done more often by accident than on purpose.