I updated the repo with a restructured version that i figured out while trying to make some themes modular that @lilbud has created.
Now a theme is split into THEMENAME-carousel.xml(Systemview) and THEMENAME-main.xml(Basic-/Detailed-/Videoview).
All theme assets are in their own folder (inside the _assetsfolder named assets-THEMENAME, Logos can be changed globally (if a theme supports it) by creating a logo-LOGOSETNAME within the _assetsfolder. The included examples also make use of an colorscheme.xml inside the theme assets folder, so it is possible to change colors. Due to some restrictions, i have not found a way yet to change colors from the config.xml in a way that i like.
The config.xml is used to change what modules you want to use.

In the next few days I'm going to try to create more detailed designs, just to see where the limit of variables is. Although i already know that some things won't work or are to complicated to set up compared to a normal theme.

Maybe @jdrassa can be convinced to loosen some of the restrictions i came across. ;) Especially when he adds the option to change elements from the ES menu, but no hurry.

Edit: Had to remove the colorscheme.xmlfor now. Need to find a better way to enable colorsets. Using variables would require to create a new one for each color in each view file. Otherwise, since they are set globally, the colorset from the systemview would also be used in the mainview.
I must check if my old code will not do that, where i had completely moved all color tags into a separate file; but ,if i remember correctly, there was also a limitation where at least one element couldn't be split up and i had to use variables.