I have a list. I've even mentioned them on the official thread. I don't have much hope of them ever being implemented, but...
Right now, my priorities are:
Put exiled cards in the exiled zone and use the "arrow when moused over" effect on cards in the exile zone to indicated which permanents (if any) are responsible for their exile. Right now, cards exiled by permanents like Ashiok and Detention Sphere sit on the battlefield. In 1v1 it isn't as big an issue, but in the cramped 2hg screen, they can cover other permanents and actually block interaction with covered cards. I've actually seen games where one player couldn't tap his lands because there were too many exiled cards sitting on the battlefield. We have an exile zone... lets use it, right?
Streamline trigger stacking. F7 only gets you so far. Cards like
Blood Artist can be hella annoying to stack because each trigger needs to be targeted, requiring 2 clicks per trigger. Having an "Always target same" option that would allow F7 to work would be a huge time saver. Also, when you have lots of triggers from multiple sources all needing to be stacked, maybe have a short cut like holding the shift key to instastack all of the same type. For example, if you have
Blood Artist,
Blade of the Bloodchief, and
Grim Haruspex in play someone sweeps killing several other creatures in addition to the Artist and Haruspex, you end up having to stack all of the Haruspex triggers, 1 at a time, then all of the Blood Artist triggers, also 1 at a time, before F7 kicks in and stacks all the Blade triggers. Being able to hold down a key while clicking on one of the triggers to have all triggers of that type get stacked would be a huge improvement.
Redo the chat interface. I could write a book on all the things wrong with the current implementation, but it boils down to that I rarely want to team up with people that I can't interact with on some other platform like Skype or Dolby Axon. Trying to manage multiple chat windows in a running game is way too hard. V3's chat wasn't perfect, but it was worlds better than this garbage.
Port some of the improvements to the 1v1 dual scene to multiplayer. We still don't get those nifty little zone icons that you can click on to expand or hide other zones.