What if Pro Motion implemented real panel docking?
Allowing the user total freedom in how he split apart or docked together individual panels/panel tabs.
Doing things like dragging the Background tab out of the Layers panel and docking it into another panel’s tab group and just docking it elsewhere as a lone panel would be possible.
This is how Visual Studio and most Adobe software works.
Recently, the dockpanel suite was brought back to life and improved. http://dockpanelsuite.com/
Maintained on github. It supports re-skinning and has a lot of features.
I know from personal experience that complex user interface dev can be a complete nightmare, but this is an area where I see a way for Pro Motion to elevate itself higher over other pixel art software and help attract more users with a more modern and user-friendly ui.
Just an idea.