"alt" notation for chords

[Rob Torop]

I found some old threads where people were talking about supporting a modifier for chords so that g:7alt would be rendered as in this example:

  

I realize that this would pose a problem for midi generation since (I think) such a chord is non-deterministic.  That is, the person comping has a choice between (sharp 5, sharp 9), (sharp 5, flat 9), and two others. I know I could just pick on and write, e.g., g:7.5-.9+, but I'd rather not.

However it's pretty common usage in jazz.

Was it decided not to do it, or is there a way?

Thanks!