They've started to be a bit braver with new machanics of late, and since the jade idol/pirate fiasco-fuck-up they've actually been getting them right, more or less. So I just want to see more of that, keep the game fresh.
I would love to see something troll and beast themed. We are also in sore need of revisiting mechs. The mechs we have no are mostly aggro oriented and limited to Mech Mage in wild.
Other things I'd love to see:
Rogue or hunter to get an actual heal.
Rogue to actually get cohesive late game control threats and tools instead of having to go tempo/combo all of the time.
Spectral Cutlass provides excellent healing in combination with Tinker's Sharpsword Oil in Wild. It's a little more challenging to make a big weapon in Standard, unless you're running Kingsbane with Lifesteal (which also is good healing).
My hope is that the decks that come out of it are NOT rock-paper-scissors. Nothing is worse than playing matches where you chances of winning are like 10% because the matchup is not in your favor. I prefer every T1/T2 deck having around a 50% chance of winning.
Support for Countess Ashmore- She's really good but most classes lack viable options for her (most classes have deathrattles, some have rush, and few have lifesteal)
This ^^^ Ashmore has so much potential but she is absolute dumpster tier right now. I expect that will change though, she has a similar vibe to Oakheart - weak on release but infinite potential to become amazing.
I'd personally like to see some more 1-2 mana cost minions with strategic implications in control/combo decks (like Arcane Artificer and Cavern Shinyfinder) as a buff to Witchwood Piper. I love the concept of Piper and think she's a brilliantly designed card who could benefit a few more decks that are looking to find their high-utility minions.