QOL:
Park: While sitting and out of combat, the Tinker can exit the mech and walk around, and even sit or stand on the mech. If the Tinker activates mech form, the "parked" mech automatically disappears.
Transformation: The mech can transform into Flight Form, Underwater form, and a Travel form. Very similar to Druids in that regard. However, instead of having a completely different form, wings or rockets would emerge from the back of the mech for flight form, or it would transform into a tank for travel form.
Decals/Customization: The Tinker should have a "garage" ability that allows them to have some customizable options. Almost like a transmog for the form. New color options, maybe some decals, maybe even the ability to swap out different parts of the vehicle. Engineering could even help in this regard by having "Mech Kits" of varying rarities that they can craft and sell to Tinkers.
Abilities:
Turbocharged: While out of combat, the Tinker in mech has increased movement speed.
Boost: Quick burst in direction the Mech is currently traveling in (2 charges)
Self Destruct!: Eject from your mech, causing it to explode dealing AoE damage. Immediately resummon a new mech with 20% health.
Buster Cannon: Merge your active turrets into the Buster cannon. The Tinker attaches the cannon to their mech and can use the cannon for a set amount of time. Requires at least 2 turrets. Cannot summon new turrets while Buster Cannon is active.
Eject! Eject 20 feet from your mech. Once activated, your mech taunts all nearby enemies. Cannot use activate mech for 15 seconds.
Escape Pod: (Talent) When you use Eject or Self Destruct, you're instantly healed for 15% of your maximum health.