Keep at it! Here's some suggestions based off my recent playthrough:
Several controls that hang out on the screen can be consolidated into their own screen/window popup. For example - upgrades for rooms and buildings. They don't need dedicated Panels, since the user wouldn't go to them regularly.
While managing different characters, you could introduce a left and right button (with tooltips! tooltip everything.) to go between them more easily. Panel elements will update when they're pressed.
Keyboard shortcuts to important opening and closing of screens would also very good.
If you're short on content ideas or busy with implementing systems and GUI stuff - try making small variations on stuff already there. Add a few levels of description to muscles, sizes, and similar things. Perhaps variations of existing events. Then, when things settle in - you know how to do that for brand new events and content.