If you go back years in the forum and look at the posts about this "GUI" this has all been said before.
To get at least themes and layouts like other application had you will have to go back to the 2000's and start there as things these days in other software are just too far ahead of what can be conceived.
It would be impossible I realize to go too modern in one step (as below videos show or as you have in the JUCE BB Plugin), but you don't just want to do another redecorate then in another 10 years do another.
At least try and get Themes and Layouts, this will let users customize what they need, simple for learning, complex, high DPI, multi monitors, touch screen etc.. PG will have to make some up that comes with the product as a choice rather than me having to make them as in the past with color/animated icon sets and other GUI elements colors etc.. for users, and maybe one other user made one up to share.

Current Modern DAW GUI User Total Customization
I'm not saying to go this modern, that is understandable with the Delphi, but there might be some ideas there, you don't want to be spending too much time having to do it for Mac also. Custom Menus might be too big a step, but basic Themes and Layouts should do for now for most users.