Keep in mind the PvE perspective... and the long term viability of your project. To demonstrate my point of view, i will let us bring back to FF11. In 2003-2004, first era of FF11.. game was simple, but PvE was at his stronguest. You had to level a job, and play your precise role in the group. You had to play that role, from level 12 to 75. It was fun, because every class was VERY needed in the group. You were gimped or you sucked at your class, the XP suffered, period.

If a player level all jobs to 50, and i mean ALL... with your idea, he can have a ''unique'' character that can do it all... Next thing you know, on long term, most people will do it.. Then where is the PvE in there ? Where is the fun if we can all be any role ? You don't need the others to play a precise role.. all members in the group will be warriors wearing strong plates, casting BLM nukes and self-heal...