Maybe there isn't a term that works for both MTFs and FTMs. The problem in the first place is that not everyone agrees with what is actually happening in a "sex change" procedure. Is the sex being changed (what is sex in the first place, legal, hormonal, genital, chromosomal, etc.)? IMHO, the gender certainly isn't being changed, since gender is mainly social. Maybe the gender is being "realigned," if you are a believer in the idea that the gender of a transsexual is the gender they always were to begin with (just with the wrong equipment). Finally, the surgery is much more than genital, since in lots of jurisdictions "the operation" entails a great many legal changes of status and rights.
Since no name really fits, it might just need inventing a new term that takes into account all these crazy contradictions without being verbose. Maybe we can invent some really dada-esque term. I think I'll call my operation "the penguin drop."
Lia