(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.

Your game statistics are replaced by the statistics of the beast, but you retain your alignment, personality, and Intelligence, Wisdom, and Charisma scores. You also retain all of your skill and saving throw proficiencies, in addition to gaining those of the creature. If the creature has the same proficiency as you and the bonus in its stat block is higher than yours, use the creature’s bonus instead of yours. If the creature has any legendary or lair actions, you can’t use them. When you transform, you assume the beast’s hit points and Hit Dice. When you revert to your normal form, you return to the number of hit points you had before you transformed. However, if you revert as a result of dropping to 0 hit points, any excess damage carries over to your normal form. For example, if you take 10 damage in animal form and have only 1 hit point left, you revert and take 9 damage. As long as the excess damage doesn’t reduce your normal form to 0 hit points, you aren’t knocked unconscious. You can’t cast spells, and your ability to speak or take any action that requires hands is limited to the capabilities of your beast form. Transforming doesn’t break your concentration on a spell you’ve already cast, however, or prevent you from taking actions that are part of a spell, such as call lightning, that you’ve already cast. You retain the benefit of any features from your class, race, or other source and can use them if the new form is physically capable of doing so. However, you can’t use any of your special senses, such as darkvision, unless your new form also has that sense. You choose whether your equipment falls to the ground in your space, merges into your new form, or is worn by it. Worn equipment functions as normal, but the GM decides whether it is practical for the new form to wear a piece of equipment, based on the creature’s shape and size. Your equipment doesn’t change size or shape to match the new form, and any equipment that the new form can’t wear must either fall to the ground or merge with it. Equipment that merges with the form has no effect until you leave the form.