The Genesis model 1 and 2 already have a red power LED that is easily changed and the model 3 is easy to add to!
If you want I can install another LED anywhere and any color you like, or a color changing LED, like this one.
$5 for single color LED.
$7 for color changing LED.
The Genesis systems already have an a/v out port with composite video and audio, all you need is the right cord, find em' cheap on ebay.
If you prefer the yellow, red, and white RCA jacks I can install them for $25.
I have done a couple s-vid mods for the Genesis, but i'm more interested in getting the component mod working since it will be much better quality. Also, s-video is still not enough of an improvement versus the cost of the mod to worthwhile.
Widening the slot will allow you to play Japanese games on your US system.
Not necessary on a Gensis 3!
Since the Genesis is an RGB capable console, a component output mod is on my list of mods to try.
I'm also going to add an overclock mod, possibly with two rates to chose from. I've ordered the part and will post results when i get it done.