If you're talking about developer machines, isn't the best(and easiest) solution to just run a VM that you administer so you can create virtual networks?
If you're talking about production machines, a userspace application wouldn't be able to sniff privileged ports without elevated permissions, so I fail to see how this application would let you get around that limitation.
No, because VMs are expensive and require some base level of system administration to operate, booting them usually requires privilege, and if the only problem you're trying to solve is reliably running (e.g.) Postgres and Redis protocol between your CLI and a server somewhere, it's extreme overkill.
imo a bit milder of a take than "just maintain a second TCP stack instead of hosting on a non-privileged port".
Also are we just ignoring that you pretended VMs were expensive to run? Most of your responses sound devoid of a lot of fundamental computer knowledge(networking and otherwise).
If you're talking about production machines, a userspace application wouldn't be able to sniff privileged ports without elevated permissions, so I fail to see how this application would let you get around that limitation.