Theoretically a Look N' Feel package can contain a Latte layout file that is loaded automatically when the user chooses that Look N' Feel.
@mart based on a discussion we had for autostarting external apps through Look N' Feel packages (e.g. Latte Dock) can we provide here the info what is needed on Plasma side and what on Latte in order to make this possible?
Latte is able in master version to import and load a layout through command line when it isnt running through command line:
latte-dock --import-layout <filename>
and of course dynamically can import and switch to any of its loaded layouts.
the latte layout file is just a text file ending with .layout.latte and it is very similar to plasma's appletsrc file.