Not yet as scantily clad catgirls are covered under the age regulations agency (I.E. if your too young for it you shouldn't have been given access to buy it in the first place)

Athough theoretically if the UK government found evidence that FFXIV was exposing teenagers to content they don't like, then they can fine CBU3 up to 10% of their global revenue (Roughly 5 billion, possibly more?) even if it's due to third party modders.

In such an event CBU3 would also be forced to enact client side mod prevention tech or have FFXIV blocked in the UK.

Of course that would be a worse case scenario in which the regulatory agency put an unreasonable level of responsibility and punishment on Square enix's desk, however it's certainly possible.