At a quick look at the score, the draft version 2 would have been able to define the staff (using the clef stafflines parameter) and the dynamics. The voices could be done using voice overlay (or several voices with specified stem direction assuming the software could overlay voices onto a single staff). The tuplets do look like a challenge for the spec, but maybe not impossible to specify. (But then, as I said earlier, there are some things that are possible with abc but that I wouldn't choose to do with it!)

Mick