There should be option to buy VIP ranks for gold collected by the player during the game. For example, VIP1 for 1000 gold, VIP2 for 3000 gold and so on.
There should be an option to fuse many weak cards of the same type to create one more powerful card of this type. I'm sure that many players have lots of pretty useless cards in their collections, but they don't want to transmute them in nexus, because they will lose them and receive one totally different card, not even similar to sacrificed cards. I know it sounds a bit chaotic, so I will describe this on example: you've got 20 useless grey (common) Icy Mist cards. You can take them to nexus and fuse them to create one green (uncommon) Icy Mist card with higher attack and defence value and +1 MC bonus. Then, if you have 20 green Icy Mists, you can create one purple (rare) Icy Mist with even higher bonuses and so on. And if there will be such thing as Card Album, these upgraded cards should be counted as one - so you don't have to collect Icy Mist card of every rarity, but only one of them.
There should be an option to create deafult equipment set for each class your character can switch to. Dressing my hero each time I change class is no pleasure at all.