Limited play for all
Arena drafting needs to be an option for normal players. It'd be a fun component to just draft and pick new cards in a less intense setting with nothing on the line. This lets newer players get into the drafting mindset without much of a consequence. They can learn how to construct a deck with the cards and tools they're given without facing any severe consequence. Not only that, it's an alternative format for players who want to get their Hearthstone on with their friends. It can be so tiring to beat up friends with the same decks repeatedly! Most of the tech is already there with the drafting engine and such. All that's needed is a way to tie it in and have it accessible for friends. Allow two people to draft their deck and provide an option to play a best out of 3 or 5 match. At the end of it, maybe save the deck. It won't be fair to allow you to keep the cards, but at least you can keep the list and refer to it.
Unique Deck IDs
A unique ID for decks is needed so that decks can be looked up and scanned quickly to ensure the submitted deck list is correct. Certain card playing programs generated a unique deck identification code. In online tournaments that I participated in, players caught using a deck with a code that didn't match the one they registered with resulted in an an automatic disqualification for the player. Even during major tournaments (real life ones), players had to submit their deck list in advance. Tools like this can help prevent cheating. There's no real way to enforce deck lists other than through an honor system.
In other games, it is certainly possible to swap cards in and out of your deck and give yourself an advantage against other specific class or deck types. However, the sideboard pool is usually limited. In Magic: the Gathering, decks consisted of 60 cards and had a 15 card sideboard pool where players could swap any of the 15 cards in that pool for cards in the main deck. In Hearthstone, there isn't really such an option. You can make adjustments in the deck editor but there is no way to enforce any kind of limit. In a tournament setting, the theory is that a player could change any card they want and add or remove anything in their class or in the neutral pile and it would take a keen eye to notice. What I'd like to see is that when players are in between matches, they have the opportunity to go to a special deck editing screen where they have the ability to add and remove cards from their sideboard pool. Perhaps a limit of 6 to 8 cards in the pool would suffice.
Hearthstone is a popular game to watch on Twitch right now. I'm not sure how much of that is due to beta-less players who are itching to get their fix, but even accounting for that, there does seem to be a demand for the ability to spectate games. It would do wonders for a competitive scene just with an observer mode feature. There would be no need at all to rely on individual player streams.
This is a similar idea to a Sit and Go tournament for poker. Have various lobbies with a maximum player sizes of 8. Once 8 players have joined and are ready, they can go in and compete in a small quick tournament done Swiss style with the top players earning gold, dust, boosters, or a combination thereof.
Here's another possible idea to spend and earn gold. Suppose players can enter a weekly tournament. Play it through all the way to the end and the ones that end up in the playoffs (or bracket round) earn varying degrees of prizes similar to the way arena matches work. On top of that, have the top winners earn a bye or a free entry into a much more prestigious monthly tournament with even larger gold prizes, booster packs, or select epic and legendary exclusive cards (maybe with alternate or gold art).
It'd be cool if there were additional multiplayer formats. The one team format I used to participate in was called two-headed giant. Two players were on the same team and they took their turn together but had a shared life pool. However, do that within Hearthstone means much more screen space would be needed. Team drafting is another fun format. I can envision that similar to the way Arena works right now except you're selecting say 60 cards (or 90, if there's three players). Then that becomes your card pool and players can assemble their 30 card decks from that pool and queue into matchmaking or challenge other teams specifically.
Speaking of team play, I was mentally throwing around the idea of how guild functions could work within Hearthstone. Other than the ability to put a guild tag in your handle and identify you as a part of a group, what possible benefits could there be? The one idea I thought of was the capability of sharing cards with people. If I wanted to offer someone to use Ysera, I could temporarily loan the card to them to use. I would still retain ownership of Ysera but once that player leaves the guild, all the loaned cards return to me. I think it'd be a nice way to "try out" cards in a deck before committing the Arcane Dust to purchase it. It also gives me something else to do with all these duplicates that I might end up with. Other than disenchanting, what else can I do with 4 copies of Sylvanas?
We probably won't see much (if any) of these features for a long time. Hearthstone is still in a beta environment and Blizzard's ensuring that all the bugs and kinks are worked out first before it gets released for the general public. Even so, one can dream!
Oh andspeaking of wishlists, can we nerf rogues yet?