With the addition of spring bones, I love the random ability to allow the springs to add so much dynamic movement in otherwise static and tedious animation.

This suggestion would simply take the spring bones gravity functionality to an object's mass.

Imagine being able to simply bring in an object or bone actor, and check a box, called "PHYSICS"

When checked, you then have options that enable:
1. SOLID (HitBox edit)
2. GRAVITY (weight and density edit)

SOLID would simply enable the objects HITBOX (a new function in composer mode, where you define the hitbox of the object/character), while Gravity gives the object/character weight, mass, friction.

This would allow us to have objects interact with each other creating even more amazing, dynamic, automated 2D animation.

You could literally drop an object and it would self animate due to having weight in the gravity. The spring bones could be setup to make it even more interesting, where it drops and hits another solid enabled object/character, creating dynamic physics in the animation.

The gravity already works great in the SPRING bones, this is simply taking an entire object, or character and adding hitboxes (just like in construct.net or game engines) and gravity to the entire object.

Example of how this works in Construct.net (2d no-code game engine)
https://youtu.be/s8srenynZO0

CTA5 has already added the needed gravity functionality in the spring bones. This simply would add a SOLID option to sprites, where we could then add a HIT BOX (the area that interacts with other solid enabled sprite hit boxes) and gravity (weight, mass, friction) where we could add amazing amounts of dynamic interactive 2D animation.