I've noticed that it's somewhat annoying for my players to always type out what they want to roll. Sure there are macro's which make things better, but maybe a graphical way to roll dice would be nice.
I'm thinking of a graphical set of dice that are on the screen (that you can turn on and off) that you choose, like a d20, d4,d10, and so on. That way only the dice you want/use will show up. Maybe a small text entry box below them for how many and any modifers like +3, -2, and so on could be added.
That way they could roll with just a click of a button.
Another nice idea would maybe be a spectator mode. So maybe a friend can watch the game but can't participate (with the option to mute/kick out spectators if they get annoying) That way they can watch, maybe learn the game and later join in if they want (with maybe a option allowing to promote from spectator to player in mid-game so maybe after a while they feel comfortable they can jump in.)
Also, a way for the GM to "pause" the game. So that way he can use the restroom, or if something happens the players can't move there tokens. I can easily see someone taking advantage of a DM in the restroom. They move their character into flanking and try to say that they where there the entire time and so on. With the game paused, the players can still chat, but they can't interact with the game beyond that. This will also help from players popping in if the DM leaves the players on a active map.