Some issues about http gateway

that we know a browser client access the content on ipfs need to use public gateway, the work flow just indicate below

that may consume a lot of gateway capacity not only cache but also the carrier broadband resource of much.

Whether can use ipfs node as http gateway , the architecture pic just like :

ipfs node N also has take the role of http gateway, that maybe ok if node has public ip , but if node located private network with private ip address, the gateway makes no sense, is it right?
Is there any kind of solution/or advice to this idea?

thanks a lot.