If anything the amount of tech debt that FFXIV has is so large I don't even know where to begin with it, from spaghetti code all the way to its systems and servers.

When it comes to removing the tech debt? That's a big undertaking if you're trying to implement something new without it messing up since bugs are abound more often than not. If anything trying to get CWPF working is a fight in itself, since you would have to have data centers connect with each other while dealing with an already constant connection between player and server(including server calls for player actions/instances).

Preventing a server crash is probably the least of their worries due to how bad some of XIV's connectivity is.