This would be a major downfall in my opinion. This is one of the reasons I play FF, and I was in an LS in FFXI where we had JP members. I like that aspect the most, we had JP runs and we had NA runs for different events, thus an event going on at everytime during the day. Also it's sweet to talk with people from all over and I'm not just saying JP, some French, German, and other countries too.
It seems to me there is a JP following though that only enjoys playing with JP...because there is this notion with NA players that we're ignorant. Which I can say was sometimes the case in FFXI, one bad apple etc... If this happens it will definately be deflating to most players on both sides.
That being said communication is key, and there is a definite need for more auto-translate which at times can be hilarious to use but works.