(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.

If any skill check is required, if you have the Vehicle Proficiency you can add your proficency bonus.

When you enter a vehicle, the following rules apply:

• You use the Strength, Dexterity, and Constitution of the vehicle.
• To use the vehicle you need to use one hand.
• The vehicle protects you, the exact effect depends on the vehicle. But if you leave the vehicle as a result of it dropping to 0 hit points, any excess damage carries over to you. For example, if you take 10 damage in tank that has only 1 hit point left, you take 9 damage. As long as the excess damage doesn’t reduce your hit points to 0, you aren’t knocked unconscious.
• Your ability to be heard, take any action that requires hands or cast spells is limited to the capabilities of the vehicle. Entering a vehicle 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 vehicle is physically capable of allowing it.

Vehicle properties:

Speed. Vehicles have the same kind of speeds of other creatures; plus few ones for Space Operas. Space Speed and Hyperspace Speed, those speeds are expressed as factor of the normal travel speed. E.g., if a destination is distant 10 space days, and your vehicle has a Space Speed of x2, then you will reach destination in 5 days.

About protection vehicles can be closed and open. A closed vehicle protects the pilot completely, any attack will damage the vehicle Hit Points; an open vehicle takes half damage, but other half is taken by the pilot.

Some vehicles allow the pilot to use some of his abilities.

• Hands. the vehicle has his own robotic hands or it is open enough to allow the pilot to use weapons, cast spells, manipolate foci…
• Form fitting. the vehicle is almost a second-skin; you can use your own Dexterity instead of the one of the vehicle.
• Brain controlled. The vehicle can be driven with the force of the mind. You need to concentrate one round to start driving the vehicle.
• Self driving the vehicle can move by itself following simple voice commands.

On destruction vehicles have one of the following effects:

• Death-trap. Once the vehicle is destroyed the wreck locks you. You are Prone, your speed becomes 0, and you cannot benefit from any bonus to your speed. To leave the death-trap you need to use an Action to pass a Strength (Athletics) or Dexterity (Acrobatics) check as contested by the vehicle Strength.
• Stable. Once the vehicle is destroyed you are Prone.
• Quick-escape. No special effect on vehicle destruction.

Mounted Combat A knight charging into battle on a warhorse, a wizard casting spells from the back of a griffon, or a cleric soaring through the sky on a pegasus all enjoy the benefits of speed and mobility that a mount can provide. A willing creature that is at least one size larger than you and that has an appropriate anatomy can serve as a mount, using the following rules.

Mounting and Dismounting Once during your move, you can mount a creature that is within 5 feet of you or dismount. Doing so costs an amount of movement equal to half your speed. For example, if your speed is 30 feet, you must spend 15 feet of movement to mount a horse. Therefore, you can't mount it if you don't have 15 feet of movement left or if your speed is 0. If an effect moves your mount against its will while you're on it, you must succeed on a DC 10 Dexterity saving throw or fall off the mount, landing prone in a space within 5 feet of it. If you're knocked prone while mounted, you must make the same saving throw. If your mount is knocked prone, you can use your reaction to dismount it as it falls and land on your feet. Otherwise, you are dismounted and fall prone in a space within 5 feet it.

Controlling a Mount While you're mounted, you have two options. You can either control the mount or allow it to act independently. Intelligent creatures, such as dragons, act independently. You can control a mount only if it has been trained to accept a rider. Domesticated horses, donkeys, and similar creatures are assumed to have such training. The initiative of a controlled mount changes to match yours when you mount it. It moves as you direct it, and it has only three action options: Dash, Disengage, and Dodge. A controlled mount can move and act even on the turn that you mount it. An independent mount retains its place in the initiative order. Bearing a rider puts no restrictions on the actions the mount can take, and it moves and acts as it wishes. It might flee from combat, rush to attack and devour a badly injured foe, or otherwise act against your wishes. In either case, if the mount provokes an opportunity attack while you're on it, the attacker can target you or the mount.