The single biggest issue holding back FFXIV needs to be specifically addressed.

[Dux]

The discussion about distance from the servers impacting network performance piqued my interest. Not being particularly fluent in network protocols or special software tools for measuring network latency I fell back on trusty ping, even if it isn't brilliant. Hopefully I got my ms to s conversions right.

A ping from UK to yahoo.co.uk took 50ms. (0.050s)
A ping from UK to yahoo.com took 48ms. (0.048s)
A ping from UK to yahoo.co.jp took 315ms. (0.315s)

The ping to the server in the US was the fastest despite it being at least an 8,000 mile round trip (asssuming the server would be hosted on the east coast). This distance is at least 10 times more than the UK maximum round trip and 0.002 of a second faster.
The ping to the server in the UK took more time than pinging the US one, not knowing the exact location of the server I am defining a maximum possible round trip from my PC as 800 miles, the UK isn't that big after all.
The ping to the server in JP was the slowest but was still a very respectable 0.3s for a round trip of 12,000 miles.

So if the average "network problem" is 5 seconds it is questionable that saving one quarter of a second (1/20th of the observed network problem) by moving the servers from Japan to some place else is going to have any noticable impact at all.