Idea is to treat (ip, port) pair as single 6-byte endpoint address. Each endpoint would be able to run just one service (well, two, one for tcp, another for udp). Type of service would be determined by looking up PTR record.
On the downside you won't be able to easily tell if two services run on a same machine or not. SSH and HTTP endpoints would be related only through DNS.
I think doing it in compatible way that doesn't require replacing routers would require NATs on both sides, and client that looks up PTR records before connecting.
Ah. That is actually an interesting idea I had never thought of. That said, it has its drawbacks as well - especially when it comes to who owns what. IPv4 are mainly all gone. So even if we tack two bytes onto each address, I'd assume those who got the allocations would get those additional addresses.
On the downside you won't be able to easily tell if two services run on a same machine or not. SSH and HTTP endpoints would be related only through DNS.
I think doing it in compatible way that doesn't require replacing routers would require NATs on both sides, and client that looks up PTR records before connecting.