face track points to puppet pin

It gets kind of messy, but you can always use Create Nulls From Paths/Nulls Follow Points and then attach a Pin to the appropriate null or even a group of nulls by averaging the position of two or more nulls. I have done that a few times. You end up with a huge stack of nulls, but you only have to write a couple of expressions to make it all work.

OK, so it is not even possible to add pin to an existing mesh.

Because the only way to add property is the "addProperty" method who takes no arguments of value and when we creating a Puppet Pin, the location of the pin has to be known at the time of its creation.

Thank you for these explanations.