I would like…
Shaman and biomechanical druids.
Paint jobs, basically unlock the ability to color your metal bits as if they were transmog pieces. They could be like in car or mech battle games where you collect the armor spray dyes. I think blizz should really consider doing this since they can’t transmog gloves, or a bunch of things below the belt. Having a way to dye your armored bits would be really appreciated to match mogs.
The ability to collect more mechanical parts through stuff like professions. Yes engineering should give us access to new cosmetics such as new arms/legs.
A hand cannon customization that changes gnomes casting animations to be like a hand cannon.
Sonething like Barret from ff7r or megaman would be nice.
It would help legitimize some stuff like shamans too since they used a whole bunch of elemental guns in mechagon with the presence of elementals. Gnomes should have access to lightning and lava magics and shoot the magics from hand guns or guns in general! Would be nice if the had a ranged racial where any of them could use guns and converts agi/str/int into each other so casters could choose to use guns for casting animations.
With Zereth Mortis I hope to see some of that first one tech as customization.
I think they should merge the cosmetics from the gnomes to get access to all the cool hairstyles and hair colors they have, and the gnomes get new hair colors hairstyles, choice of racials and mech part replacements.
I hope we get full robot customization like northrend mechagnomes.
Would be nice if they could inspire customization based on Exos form destiny. At least how the eye colors are done and the different head shapes for the full robot look.
For melee would be nice to get like fma or Alita: Battle Angel sort of mechanical arm weapons.
For Zereth Mortis we now have some machine-like life forms that seem very natural so I think if mechagnome druids ever became a thing these would be nice options to base there looks off of First one stuff.
Would be nice if We got the Sombra hairstyle on more races. With the mechagnomes I would like something like her hacking hardware tattoos as well.
Symmetra and Overwatch cast has nice cybernetic parts. Her arm shows there is much diversity and styles they can add to stuff like mechanical arm customization by giving us more options like see through titan tech for example.
The circular piece in Symmetra’s arm could also be use to signify an outland for a standard mechanical sort of gun for unique mechagnome customizations too.
I think if they worked on a way for gun’s to be used as casting animations for races that would be a nice race fantasy. I could see mechagnomes pulling of gun mages sort of things for certain classes. Lord Godfrey from Shadowfang keep already uses guns for his spells and that would just be a nice ingame thing to have.