Well, I only have two and they potentially aren't small, particularly from a dev standpoint, but I think they'd be nice.
1. Fully customizable scrollable track sections. Here's what I mean: Right now there are three scrollable track sections, one for tracks, one for busses and one for mains. I really like this. Scrolling through busses without scrolling your tracks in CV is really great. What I'd like is the abiity to put any kind of track in any section, AND to be able to configure the number of sections. So by default it would work exactly as it currently does. But then perhaps you have a top and bottom snare mic that you'd like to send to a "snare" bus and then to the drums bus. You could put that snare bus right next to the tracks that feed it, but still have that snare bus feed a drum bus in the "bus" section of the mixer. Then, for example, you want to use ARC or some other "monitoring" effect. You could create a new section, put the ARC bus in it, bus the master track to it, but still not clutter up your existing "bus" section. Defaults could be set so that busses end up in one section by default and tracks in another (again, replicating existing behavior), but busses and tracks could be moved around freely.
2. Bus freeze. Remember back before we had a freeze function we had to bounce tracks? We still have to do that with busses if we want to free up their resources. It'd be really cool to be able to "freeze" a bus so that the audio that is routed to it gets bounced down on to the bus track, sources get archived and FX bypassed without creating a new track in the track view. Essentially it would "convert" the bus to an audio track that lived in the bus section and allow unfreeze just like track freeze does.
Dean