(Paolo) Shamans have the ability to transform in their spirit animal. However the ability does not scale with level. While it is true that most racial abilities do not scale, I see this ability akin to the Dragonbonrn's breath weapon. What about adding something like:

To the stat block of the animal?

(Paolo, Work in Progress) Vehicles are basically considered a second skin, just like Druid Wild Shapes.Depending on the vehicle (fully closed or partly open) it will works exactly as Druid Wild Shape or split the damage à la Shield Guardian.

If the vehicle allows to use larger weapons we convert the dice following the table. The damage changes are inspired by the Spell Enlarge/Reduce.

For example, let us think to a Mecha Large robot with a Battleaxe. A Battleaxe normally deals 1d8 damage (1d10 two handed), in the hand of the Mecha the Large Battleaxe will deal 1d12 or 2d8.