The thing about online depends on the difference between releases. Melee wouldn't work for global online, because the PAL version had some rebalancing, which made the game mechanics a bit different(for example, Marth weighs less in the PAL version). If we were to have worldwide, Nintendo wouldn't be able to do that.
If however, the game was the same in all versions, I could see that happening.
If however, the game was the same in all versions, I could see that happening.