Definitely top priority for me would be a per articulation negative track delay within Expression Maps.
Also, it would be great to be use Logical Editor for Expression Map articulation work in MIDI (e.g. Select All Articulation Name “Staccato”).
As @Teo and @Dewdman42 (and possibly others) mentioned, a DP-esque Chunks feature would be wholly game-changing for scoring longer form media projects.
These three things would be huge and fantastic.