Hello, and thank you for the suggestion.
The reason the blending modes we support are limited to the ones you can find here: spine-scripts/photoshop at master · EsotericSoftware/spine-scripts
is because we have to ensure said blending modes are compatible across all runtimes. Unfortunately, overlay and color dodge cannot be widely supported at the moment.
Regarding clipping, it can already be parented to a bone, and you can even weight it to follow multiple bones. You can read more about it in the user guide:
Clipping - Spine User Guide
Clipping is an expensive operation on the CPU as most runtimes don't support stencil buffer access or masking, but if you are using the Unity runtime, this article may be interesting for you: Blog: Unity SpriteMask and RectMask2D support