Would rather let people be a half-snake woman with snake hair and a daily, temporary paralysis eye-ray.
See, this is what doesn't make sense to me. Why do all the other medusae in the world get permanent petrifying gazes, poisonous snake hair, and whatever other abilities innate to their species, but the character isn't given them? Was she born with some sort of disabling condition? Are there two species of medusa, and the player's character happens to be from the "lesser medusa" subrace?
I actually don't have a problem if the answer to either of those is "yes." What I have a problem with is when there
isn't an answer to that--when it's just, "no reason, that's just how we roll." I can't see that making sense with the level of world-immersion many people (including myself) play with.
Maybe it really is an issue with how casual your D&D is. If you aren't really worrying about deep immersion, the fact that your PC member of the race lacks the innate supernatural features all of his friends and neighbors were born with isn't an issue. I just don't enjoy running or playing in that type of game.
I'm a D&D simulationist. That's just how I roll. I'm automatically going to reject any explanation that ignores that. Fortunately, I think the designers this time around actually tried to accommodate that. Basically, it seems like they were saying to themselves, "let's make it so that simulationists and non-simulationists can both customize it and enjoy it without much trouble." Feats to add special abilities to races, and actual lore with the feats saying, "not all members of the race have these abilities" is a great way to handle it. Drow commoners can't cast
darkness. Svirfneblin commoners don't get the suite of spells. It requires special training (represented either by the advancement in the MM stats, or by class levels or feats) to get those. It's up to an individual PC whether he wants to learn to do those things or not.
Excellent framework, and I hope they stick with it.