Suggestion #1: Dynamic Income
The suggestion is that the rating amount of coins you win for your arena beating someone should scale with the remaining health, just as the score and amount of coins you win for winning a battle scales with your remaining HP.
To be specific:
Right now, the base values for people under Top 10 are 2, 3, 5, and 10.
Since no one really builds EM decks for the AI, you can assume that they'll get less income if those were the maximum values for non-EMs. Therefore, the amount should double to 4, 6, 10, and 20 for 100hp decks. That's 1 coin for every 25 final HP, 1 coin for every 16 final HP, 1 coin for every 10 final HP, and 1 coin for every 5 final HP...With the reward doubled upon EM. That gives the max for a rank 11+ platinum with no max-hp-increase cards to 80. I want rating to be determined like score is, so losing penalty should obviously be doubled (since we don't want farms) to 8, 12, 20, and 40.
I'm sure that this is possible, as the Arena is unsynchronized PvP. If it works for both players in PvP, why shouldn't it work for your Arena deck?
I haven't seen myself losing wins, which means that your Arena wins/losses are updated after the game, after the necessary information for this feature is known to the server. This makes the feature suggested feasible to program.
Now, are the rewards for the implementation of this feature worth the time it takes to implement it? Probably not. However, I think that it would make it better than the current "If you lose two (close or otherwise) games, you're out of the Arena forever."
Suggestion #2: Restricted HP
The suggestion is that Bronze must have 75-125 HP, Silver must have 100-150 HP, Gold 125-175 HP, Platinum 150-200.
In addition, with the difference between Silver and Gold being large (ability to win unupped/upped rare spins), I think that dexterity should be restricted to only Gold and Platinum decks.
This includes the suggestion to give everyone 4 extra skill points, so that Level 1 starts at 5 points. Each League deck starts with the minimum HP, and can spend a total of 10 points in HP to reach the max limit.
Currently, Arena is VERY DIFFICULT to farm, not because the decks are hard per se but because it's difficult to build decks catered to taking down both 100 HP opponents and 200 HP opponents. I think that differentiating the leagues, just like differentiating PvP1 and PvP2 or differentiating AI3 and AI5, would not make the games more boring for the players.
Suggestion #3: Sideboard
You should be able to take out up to 30 cards from your (60-card) deck after seeing the opponent's mark+card+stats, (the opponent's deck, or a random selection of half the cards in the deck).