Yer probably out of luck. Even if there was a solution, it'd be quite complicated. IDK about FFXIV but most apps and games, you cant simply just copy the install folder to another computer and it work, because the install creates registry entries in windows that are not copied by simply doing this.

Your employer probably has a firewall set up with their network hub or router that will block the ports needed to play the game.

And if you COULD actually get it to work, I'd imagine it would run like poo, if even at all with the files on a USB stick instead of the internal storage because of the extremely slow access to a USB stick, and on top of that, if the work PC doesn't have a dedicated GPU, it would, for the most part, not be playable, and very slow and choppy. The only real IGPU that can even begin to handle FFXIV is an APU processor from AMD.

Anybody feel free to chime in if I'm wrong.