Thanks a lot for the feedback! I will be pushing update 1.3 in the coming days and will publish a better integration overview alongside with it that should help you integrate the essentials into any existing project! 
Update 1.3 will include
- a better building system that allows direct placement of objects with a preview mode as requested
- multiple floors, and more modular restaurant management. You can have staff assigned to different service hatches, so that one waiter will only serve floor 1, another will serve floor 2 etc!
I will write here as soon as the update is available!
Cheers