I actually really like the idea of putting the timeline controls in a separate tab next to "PALETTE." Keeps the map area clean, and it fits naturally with the current layout.
Only thing I'd suggest is making sure it's easy to find and quick to access, especially for people who are constantly scrubbing through frames. Maybe it could have the option to pop out or float if someone wants it on the side or elsewhere on the screen temporarily? I know you have UI elements that are flexible in moving around so it would be neat to have that as well.
Overall though, the design is looking amazing. Its very clean and accessible without blocking the data.
Look forward to hearing your thoughts on this.