I'd honestly prefer a female Link to have very little differences from her male counterpart. She should have the same iconic features - long ears, epic sideburns, parted hair, etc. - and the only differences being that she has more obvious feminine features, like a slightly slimmer, shapely figure. They don't need to put her in a cute outfit to make it obvious that she's a girl. She should be treated with the same respect as male Link.
Epic side burns? On a girl? Hm.. it could work lol. I think as it stands, Link does look a bit girly, especially in TP, and adult OoT. His belt defines his waist quite well, and the dude is wearing a freakin' skirt with those toned ass legs. 
I actually think it would be neat to have the choice to play as a female incarnation of Link. I also disagree with others to an extent, cause I don't think there should be much narrative change based on gender. I dunno though, I guess it could be done well, and they could even do a "second quest" type thing, but that's pushing it. Either way, if I do have a reason to replay the game as another character, I would. If there is an option, I'm totally playing as female Link. I dunno why, but in most games, I always choose to play as a girl, if I can lol.
I feel like they are going to do something like what they planned for OoT with having different arrows, or as Miyamoto called it at one point in OoT's development, "magic missiles". OoT's medallions were originally going to be used to power up the arrows with their respective element. Forest was wind, (possibly regular arrows), and Water was Ice at that point. [source] (<- This is actually really interesting). I'm thinking this cause in the trailer they show off the bow and arrow, and we still haven't seen any sword combat yet.
One mechanic change I think would be neat is being able to run, and slash (a la TP) but also, move, and attack, in general without stopping once you connect with an enemy, if that makes sense.