The executable is located in C:\Program Files\Mendix\Mendix x.y.z\modeler
I am working on a module for the appstore. In this module you can either create or upload an mpk package and set all the nodes you want to upgrade. You can then either do a direct upgrade of all those nodes or set a scheduled event that triggers the upgrade proces.
We have the same requirement because most of our clients all use the same model so I also need to deploy to more nodes the more clients we get. And the documentation is in the deployment API. The module is partly working (upload an mpk and it will deploy), but not appstore ready. I need to add error logging and I still need to protect the API key you use. I am currently building the building a package part. And I asked some questions to Mendix support because I think there are still some bugs in the API. When I upload a package for instance to a node the name stays empty. I expect some answers from Mendix this week to see if I did something wrong or that it is indeed a bug.
I hope to have some time this week so I can give you an early beta soon. I will make a github project when I am finished.