FFXI didn't actually 'influence FFXII', as it didn't have to - FFXII was originally conceived to be exactly like FFXI - as in, a MMORPG. It was first announced back at the Squaresoft Millennium Event in 1999, when it was stated that from FFXI and onwards, the series would be practically online only. Of course after Sakaguichi left those plans were pretty much dumped, but hints of the online plans for FFX and XII can still be seen, such as the PlayOnline branding on FFX's title screen, and the GUI and many other elements of FFXII being very much like a MMO. But I digress.