I understand that you do not question the extra fees. But your definition says it all. ''While more advanced features must be paid for". Installing an extension for someone is not a feature. There is not extra feature that it gains. The service is not even related to the module itself. It is service that we offer as a Magento development agency for all our own extensions and third party extensions.
It is a cross sell service that we provide (not an upsell). While necessary services like Support remain free on this module.
A really clear example would be Spotify. Spotify uses a freemium model to get customers. They offer a product but without a lot of features. If you want those features you are expected to go Premium. Now lets say Spotify was totally free but a customer would need some help installing the program and gets charged for the installation of the free software.
The software itself is still a free product but a cross sell happened. If Spotify then would make the software almost impossible to install and it would require their specific expertise then it would be a form of Freemium.
This is exactly the reason why we provide free support on the extension. We believe that giving back to the community is an important thing since Magento thrives on its open source community.
If we wanted a Freemium model then we would charge for extra months of support.
Interesting discussion though since there is a fine line between what is and what is not Freemium.
This topic was more intended to see what the community would like from extra features that we could add (for free) and publish.