I honestly think there are enough classes in the game as ist - there should already be a class for every playstyle (support, tank, ranged, melee, ranged caster, melee caster).
Personally, I wish the devs would focus on companions with more personality (more interjections, more comments on events, deeper personal quests [perhaps even more than exactly one quest per companion], having actual relationships [not necessarily a romance, although that would be okay, too, but developing friendships, or growing animosity, etc.], companions leaving the group if you make decisions going against the moral code of a companion, these kind of things).
Generally, I'd like to have a more immersive game world with more reactivity to the PC's class/race/ethnicity/gender/social status (more than the otherwise meaningless sentence here or there), perhaps with whole quests or other situations specific to certain classes/races/etc.
Both concepts could even be combined. For example, right now I'm playing a clergyman from Aedyr, a Priest of Eothas, who specifically came to the Dyrwood to (again) spread the Eothasian belief. But Durance had nothing(!) to say about that (not even during the temple quest in Gilded Vale), which is kind of sad and imersion-breaking.
Or an Orlan PC could have to deal with (a lot of) racial prejudice, a PC from the Vailian Republics could get a quest specific to Vailians (like Pallegina does now), there could be a Brotherhood and/or a Sisterhood (like the Frermàs mes Canc Suolias), only open to members of all classes, but only to men/women, the PC might want to join during the course of the game, and where the PC has to prove his/her worth and reliability, and so on...