I think not having Link speak so that the character can "relate to him" is a piss-poor excuse. That's like saying it's easier to "relate" to those da*n "Choose Your Own Adventure!" Goosebumps novels better than classic, well-written literature.
Obviously, I'm in the "Link needs to start speaking" camp, or the "Zelda games need voice acting for the other characters, at least" camp. If it was handled well, with believable dialogue, it wouldn't detract from Link's appeal at all. I mean, because though he may not be speaking we all know what his voice sounds like. And how many of you are really "relating" to a mute guy with long blond hair, pointy ears and tights who must save a world full of other elf-like people, humans, and alien-like creatures by collecting items from a bunch of random temples? As a black guy from Los Angeles I know I'm not "relating" to him: I'm just controlling a character (in 3rd person, no less) that develops in every other way that establishes him as an individual character BUT speaking. I would be relating to him more if he were a more complete character, that did speak, who made me relate to him through the value of his own opinions and voice.
Pro:
Obviously, Mario Party would have to have a different mode for online. Something similar to the rapid back-to-back format of WarioWare. If they did that, Mario Party would work pretty well online.