I know one thing you (probably) don't: jjSTREAM isn't allowed to open files with certain filenames, for example a script can't open admin.ini and leak the passwords. In theory, then, this hypothetical jjIPADDR could save files with predictable filenames that jjSTREAM could not open. But I'm pretty sure that if your script saves IP addresses to the disk, you want your script to be able to read those same IP addresses again? It's just broadcasting them to clients that's bad, and yes. unblockable.

Instead, let's ask "What problem are we trying to solve?"

Fabian offers two use cases, from what I can tell.

Here's where we get into "host your own server" territory. Any server that offers the /ip command to (some or all of) its remote admins does so (one hopes) deliberately, and by joining that server, you are agreeing to let them see your IP address. If you want a roleplay server where everyone is really anonymous (except to the server, that's just how the internet works), you really need to host (or otherwise find) a server that doesn't allow /ip.

I assume "identify" means "count" here, and Fabian wants to count how many different IP addresses are joining a given server over a given period of time, and using the number of IP addresses as a proxy for the number of distinct human beings. You don't need IP addresses for this, just UIDs! The client checks for a mymutator-uid.asdat file, and if they don't have one already, the server generates a new unused number for them and sends it to the client, who saves it as mymutator-uid.asdat.

Obviously it's possible to game this system, like a client could delete their uid file if they wanted to inflate the numbers. But a) clients can change their IP addresses too and b) why would anyone want to do that? who benefits from inflating the server's statistics with fake players?