If you're talking about SR5, you can probably make these work for most characters with clever use of negative qualities and some roleplaying.
- incredibly aged characters: Poor physical stats, the Weakened Immune System qualitiy, the Unsteady Hands quality (the books specifically mentions advanced age as a cause of this NQ).
- characters with some sort of disease (is it a new disease, infectious, were they born with it) Weakened Immune System can easily be re-fluffed as HIV or something similar. Poor Body and Strength to represent physical weakness. For infectious diseases, you'd pretty much treat this as a toxin, I think there might be rules in the book for this somewhere but I'm not sure.
- crippling injuries Again, poor physical stats. Perhaps unsteady hands, Incompetent: Close Combat, Incompetent: Firearms, give them the equivalent of a cyberlimb with 1s in Strength and Agility to represent a particular limb that is crippled.
- mental disabilities/injuries (addressed a little in some of the rules books but not enough how do you build on it) Low Logic, Intuition, and possibly Charisma. Uneducated and possibly Uncouth NQs.
- playing with metahumans (yes he's a troll but his mom is human so it might affect his stats like thus) I don't necessarily think having human parents would affect a metahuman at all, but again, just keep stuff like Body and Strength at the racial minimum and maybe give them Exceptional Attribute: Charisma to show that they're "prettier" than the average trog.