What would be tremendously helpful would be a tool that allows the user to select every other item in a time series, or the second item in a set of four, and so on. Sitting here and selecting each high hat note, or each arpeggio note that needs to be adjusted in a stretch of notes across eight bars is a big sink of time without this tool that other apps have. It should just work for any item on a timeline, not just notes. Live has a great workflow but it comes to a stop right here. Similarly, it would be good to be able to split notes, but it's this selection process that really gets me.
Of second priority would be having a MIDI list editor like all other apps. I know this has been pointed out over and over again, but it bears repeating. There are too many situation where nothing beats being able to just punch in the number and have the entire selection jump to the value without fiddling with the mouse and squinting at the graph. I love Live but this stuff drives me nuts.