Cleon, in theory (and very definitely in real life) I agree with you about the players occupying the same space, however (and this has been a problem I've had with the game since they did away with wibble/wobble) central players tend to stick too much to the side of the pitch they are on.
i.e. I want to play 2 MC's, but because that means lining them up one alongside each other for display purposes on the positions layout, they end up playing like and inside left and inside right. I'd rather they operated more centrally than they do.
07 is certainly an improvement on this than 06, but it's still there, and so much so that I always try and have a right-footer and a left-footer.