improve 2d stabilization

with the improvement of the VSE editor, i have started to use blender as a video editor to edit real footage. while i know this is not a focus for blender, i enjoy using a familiar interface for some new tasks. while using the VSE, i can recreate many effects and corrections that are missing with the compositor nodes, very nice!

the only thing that i could not replace yet is a solid stabilization solution. while using the motion tracking and the 2d stabilize node is nice, there are some features that would help it improve a lot:

• adding shear and non-uniform scaling to the existing options (position, rotation, scale) would help stabilize footage with a rolling shutter much better.
• allowing to automatically create a smooth camera follow would be nice. this would smoot out the camera motion to a smooth follow, using gaussian or cinematic-L1 with a variable smoothness.

here is a proposal on how these additional options could look in the UI:

currently, i am using a python script to work around the smoothing. the script sets a target position keyframe every few frames, resulting in a smooth camera follow.