Lupin did a good list, heres mine. And if you say "you can do this with a module" I will scream.
1. Basically my entire (lt) Live Monitor module should be baked into the main GUI.
i.e. layer thumbnails, individual layer play/pause, fader controls (cut/take) + output fade control.
2. Lock Layers! Please oh please oh please.
3. Second Preview Window (main out/preview out)
4. Minimise the 'master' panel at bottom of main GUI.
5. Ability to right click on any control and 'Set state as default'
6. 64bit - 4gb+ RAM access.
7. Merge projects.
8. 2-way Midi baked in - Particularly so we can send states to & from modules without learning to code it manually. Basically if a midi note is set to a knob/dial/button - it should send the position as well as receive it.
9. All the GUI buttons that aren't assignable to KB/Midi/OSC need to be (preview controls are an example).
10. Allow a latching setting to midi for controllers that don't/can't do it by default.
11. Transform controls in preview window. Kinda like Photoshop's command-T - easy, quick reshaping/moving/distortion.
12. A timeline!
13. Larger media set window - maybe just allow to drag down/right to add new rows/columns.
14. Syphon out + 2nd Monitor out option - currently it's just one or the other. Then we can record to syphon and still vj or one day allow networked syphon output to other comps while still outputting from primary out.
15. Window snapping
16. Less flakey Midi, Keyboard, window layout saving. It works but it just doesn't feel solid, mainly as I half to use uarts 2way midi for main UI mapping and then the normal way for module mapping.
17. Multi touch? Pinch to zoom for scale maybe? Or double click on a control and then allow focused drag up/down (dial rotations).
18. Improved module editor. More control options/variations. More intuitive GUI layout. Undo. Serialisation info - maybe show added dict rules in a panel so I can see what is getting written or not. I don't know much coding but I feel the Module editor makes it harder than it should be do some of this stuff.
19. Quit dialogue that offers to Save or update saved project as well as Yes/No to quit.
20. Guides with snapping on preview. When using a triplehead2go it would be good to have assignable guides to show where the screens are getting split. I rarely use the TH2Go to make a 1x3 screen but often have 1x2 and then a separate 3rd screen (yay layers) and have no way of know when a clip is 'leaking' over to the other screens.
If anyone agrees with any/all of these please do comment.