I figured that was going to come up. Are we talking about Dolphin? Widescreen support has already been a part of that for a while, hasn't it?
There has been a widescreen hack for a few years. It is garbage and messes up the shaders in the game.
IE (the dude I'm working on Melee:Online with) has devised a method by which to change the camera FoV so the shaders are stretched correctly to the widescreen aspect ratios.
He and I are also working on high resolution HUD textures to augment this.
The FoV fix is a simple AR code you can apply through dolphin and the HUD textures will be forthcoming in the near future, I'm sure.
We've also ironed out most of the kinks from PC emulation, most people should be able to run the game just fine(locally) on their PCs using an updated shadercache file and a gamespeed fix (if you machine is pokey). I plan on having an HD melee setup on my basement widescreen whenever I get some more GCN>USB adapters.