1) Playable Goblins
2) More voice options with accents
3) Difficulty settings
At any stage of development, I'm new to this type of game and I don't know anything about the D&D rule book that this is closely following so not sure if Goblins are just obviously ruled out.
These are just some things I'd like to see personally
1) Pretty unlikely, but half-orcs are a distinct possibility as they are in the standard Player Handbook.
2) Almost guaranteed; the resource requirement to add these is made massively easier by their decision to have silent protagonists, as a voice option only requires a few dozen flavour lines. I dislike that decision personally as I regularly feel like I'm roleplaying a drow ranger who also dabbles as an amateur dramatics mime artist, but that's just me. More voice options would placate me on that to a large degree though, if there are enough.
3) I'd be amazed if there aren't any, even if it's limited to a slider that ranges from -3 to +3 on dice rolls: but I'd EXPECT a good deal more versatile options than that such as; playing with or without elevation advantage mechanics; allowing bonus actions to be used with an action slot; refreshing spell slots on a short rest; making Shove and Hide an Action rather than a Bonus Action. Such difficulty settings would be BY FAR the easiest way for them to dodge the criticism from the actual 5e role play crowd whilst still producing a game with enough potential ADHD to cater to a mass market.