Yes, I do think that qualifies. Being under-employed is significant, and "underemployed" can even mean someone who academically has a PhD working at the same level as people with bachelor's degrees because of social delays.
I kind of like it. I would prefer not to have it linked so much to IQ, though, because we still have the problem of someone with, say, Down syndrome and an ASD, being rated "severe" when it's actually that he's got global stuff going on that means you've got speech and self help skills coming in slower anyway. Second IQ gripe: It's often really hard to measure IQs in autistic people, and IQs are only loosely connected to ability to function in the community anyway. We've got autistic geniuses who need round the clock care, and people in the MR range who are living on their own with minimal supports; in between there's people with genius IQs who need moderate support and people with average IQs who somehow have advanced degrees thanks to Aspie perseveration... IQ really shouldn't be tied to it. Functional level--the level at which you can take care of yourself--would make more sense; like the intermittent, limited, intensive, pervasive scale.
If you categorize by functioning level, you end up with people who are strongly ASD lumped in with people who are mildly ASD and have some other disability.
If you categorize by ASD severity, you can't predict how much help they will need because of co-morbids and such.
So you need to yank that GAF out of axis 5 and stick it next to the ASD level as a "support level", like so:
Examples to illustrate what I'm thinking of--
"Moderate ASD, limited support"--person who can't drive or live on their own, but does fine in their own apartment with assistance in cooking, shopping, and a decent transportation service
"Mild ASD, pervasive support"--a child with developmental delay and mild autistic traits, who requires a great deal of help to take care of himself but only has mild communication deficits and repetitive behaviors
"Severe ASD, limited support"--Good self help skills, but no speech or ability to socialize, and self-care skills are only used in the context of a routine that is identical from time to time--may actually have a very high IQ, if testable; needs someone to help clean apartment, cook, shop, etc.
"Mild ASD, intermittent support"--Adult autistic, requires help with education and/or job placement, possibly with transportation or access to counselor/coach
"Severe ASD, pervasive suport"--Nonverbal, difficulty taking care of themselves, probably has SIBs to watch out for, huge executive dysfunction and sensory issues. Communicates via text to speech device; may have high IQ or isolated savant-like talent despite daily difficulty.
See what I mean? This would be a truly helpful diagnosis. It would define the strength of the ASD symptoms, and predict how much help the person needs, but it wouldn't categorize based on IQ because the IQ really can be all over the board within these categories! If severity<support, one can assume there is global developmental delay or another disability involved.