I think there is some merit to this idea. Things have changed compared to what we knew on the 1st day of announcement (since we can now likely expect a standalone version of the IDE and not just a browser based version).
If the subscription were rent to own, perhaps after a certain amount of years subscribing you could own the standalone IDE. You could still subscribe for the web-based IDE and cloud services, but if you didn't want them you could keep the standalone IDE and lose access to the web version/cloud services.
Or, at least reduce the subscription fee to something minimal, at that point, if you chose (still with loss of access to the web IDE/cloud services).
Once you reached that point, perhaps after a year or two they could release C4 and start that all over again.