The following features should be added:
A test draw feature. This is particularly useful for fine tuning deck building features. Many third-party sites include a test draw engine.
The ability to join a game and THEN slowly choose your deck. Right now, the process requires an almost snap judgment. Much better to join the game and then choose the deck rather than choose a deck to join a game.
Player history notes tracking players. It would be helpful if I could “tag” my matches with a note about the player so that I have their deck history. When I join a match with that player, the first thing that would appear is their player history note. Right now, I feel blind sided by the myriad of single player matchmaking system in which my ability to remember who I played against and what they were running in a sea of anonymous gaming. If as I suggested, you could join a match, the player history came up with a personalized note (Plays Delver), then I could choose the appropriate deck to play against the player (assuming they played Delver again). This would reduce the netdecking and deck monotany a lot.
The Momir Vig Avatar should be included in the core set of the game purchase. Many game companies allow mods to their games and even distribute such mods for free (Black Mesa on Steam for example).
On a somewhat related note, the overall pricing schemes tend to deter players from exploring additional products, such as Planeschase. My understanding was that a form of Planeschase was included for free in the most recent version of DOTP 2013 which was selling for only $4.99 on Steam during the Steam sale. I'm tired of having to try to cobble together duplicative collections across a wide variety of products. MTGO should be a one-stop solution for Magic players. I also feel that developing multiple titles that try to do the same thing means each individual project gets short-changed.
A way to practice draft for free. I feel more players might be interested in drafting if they could practice drafts to get comfortable drafting. Currently, the only option for players to test draft for free are third party tools.