These ideas have been explored as far back (if not further) as 9 years ago - try searching around for CHI groups (e.g. UIST 2012) playing with the synaptics forcepad (which had depth sensitivity but lacked a piezo feedback):

https://www.youtube.com/results?search_query=chi+synaptics+f...

https://www.youtube.com/results?search_query=uist+2012+force...

here's one specific to layer selection: https://www.youtube.com/watch?v=CK2AzhmifTk