I honestly think that this game could use some more microtransactions, aside from just purchasing packs and missions.
Things that could be sold:
-Extra deck slots
-Choose your default color/Secondary color if you lose the coinflip if the other player purchased the same color.
-Unique looking units/HQ/starting hex images - Same units, cooler/unique looking models
-Turn x cards into foil cards - Everybody likes shiny things.
-Reserve time (up to a certain amount)
-Experience boosts (although experience currently doesn't really give you anything... could be changed)
-Single player/Coop only cards - Not usable during pvp games, powerful ally cards that you can use to turn the tide. (Show the whole map for a turn, special hero units, multiple unit heals etc)
- Access to a map maker
Keep in mind that microtransactions should be just that... it shouldn't go much over 3 or 4 dollars for each thing. Depending on what is added premium players should either get things for free as long as they are premium or get a substantial discount to entice people to purchase premium.