Would you pay to be a power user who can invite and manage say a dozen family & friends?

In this model it might be possible to assist uptake by having a class of power user who can manage their group over onto an ad free network.

Example: I have a private github account with repos I share with various friends who are not paying github users but are nonetheless now engaged in the github platform.

Yes, this is an under-appreciated idea that may be critical to having the whole thing work. If it's a paid service users should be able to pay for other users to use it.

WhatsApp had this. :-/

That's not a terrible idea. You might also give some users free access if they're net-beneficial to the network