I don't know if the ir lasers are safe even dimmed or I would have already done it. In regards to the camera, like I said, the ps3 camera uses custom drivers.... we don't want that because if a windows update breaks the drivers we are at the mercy of whoever wrote those drivers to get it working again. imho it needs to be a HID camera so no drivers are necessary and, theoretically at least, it'll work for years to come without hassle.
640x480 sounds adequate, but I don't know if it is. With the camera mounted perfectly where the monitor is straight on and fills the screen we have a resolution of 640x480... which will work for most games, but realistically, to mount the camera on a standard mame cab while getting the whole screen in there, the alignment isn't going to be ideal.... It'll view the monitor at an angle, possibly an extreme angle, which means that one side of the monitor is only going to take up a percentage of the screen, and whatever percentage that is, it'll be the maximum resolution of that area. So realistically you'll probably get a useable resolution of 320x240, which, again, is probably ok for old games, but it might not be enough for newer pc games. Mind you there aren't a lot of pc based games, but occasionally we'll get a gem released like typing (house) of the dead overkill. That games logic is 640x480 (the resolution of the wii, where it was originally released) so we've potentially halved the gun's resolution.
I do think it's doable, but it'll be more complex than you think. If you guys want to get together a parts list I would be willing to try, but I don't want to spend a lot of money. Assuming these guns are released, they don't seem super expensive to me.