My completely unoriginal, stolen from other games idea for a Tinkerer class in the next expansion:
Roles: Tank / Range DPS / Healer (because I think every new class should be all roles so we have more roles available out there)
Replace Tank with Melee DPS I guess if they dont want another tank, or if they want to be cute, add another 4 spec class like druids have. Anyway:
Tank / Melee - Mech mode
You fight in a mech all the time, not unlike the various mech mounts we have been getting over the years. Various melee type skills, rocket punch, death from above style skill, mines, missiles, etc. No pets or turrets.
Range DPS - Summons baby (im a pet fanboy as some of you know)
This would be all about summons. Turrets and pets. Gun turret (max 2 out), Missile turret (max 1 out), robot pet (max 1 out, dps or tank variety). You do more damage if you are near your turrets. Skill to relocate them for movement fights because they are stationary.
Range skills would be sniper rifle type shots (to direct all damge to the mob you want for example), and some granades or missiles and whatnot. Maybe air drones doing a strafing run. Big cooldown skill to overcharge your gadgets to do more damage / faster attack speed.
Healer - gadgets healer
Kinda like the range, except with healing turrets. No pets tho. Healing turret (max 2 out so you can have one in range, one in melee), these would last a long time, 20 secs or so? Healing drones, max 1 out, maybe more with talents. Long duration HOT that is a drone that sticks to a character (like a tank) and constantly heals him throughout the fight, you can relocate the drone to another character (visually like the healing drones from the Old Republic healer because I fucking LOVED tht visual). And now the big one, which I love and would never work because players are idiots.
Health packs, you can drop healthpacks throughout the combat zone and people need to walk over them (I wont even say click) to heal themselves. Very short cooldown (1 sec?), no limit, or a big limit, like...I dunno, 10 or 15 out there.
Races I guess Gnome and Goblin, even if I hate the idea of just 2 races. Humans and...orcs also maybe?