Thunderwing. I think I get you now. I totally get where you are coming from. and understand it.
I, on the other hand, am totally different from you. I wouldn't choose anything. Anything that makes us different, anything that makes life more difficult. I would choose the easy life, given half a chance. I wouldn't choose diabetes for myself, I wouldn't choose asd for ds1.
Mrs Oblomov (this is a joke btw) lets choose the characteristics for your next baby ( I am unable to, and do not desire any more children, but lets pretend):
boy or girl - don't mind, maybe a girl, because I don't have one?
tall or short? medium please
fat or thin? medium please - hourglass figure please
very clever or thick as shit? what do you think? 
ginger? no, I've already got one(he's extremely ginger proud, but that's not the point), no to that please.
glasses? no, all of us wear them, no thanks
perfect teeth or a lifetimes worth of dental work? perfect please
any medical conditions? preference for ASD etc? ........ no thanks. no to all.
Depends on the person. Depends how strong you are. We can all cope with varying degrees of difficulty. Some of the things I read on the SN board, where people have life much more difficult than I do, reminds me.....
do you remember years ago, cant remember the poster, her cerebral palsy dd, having fits all night every night, respite was removed. FFS. That hit me hard. My life aint as easy as some, but its a lot easier than many. sometimes I forget that, I get so self centred, I cant see the bigger picture.