I don't think the delay between ZorinOS releases is such a big deal. Just about everyone I install ZorinOS for doesn't know what Ubuntu even is. From their perspective, they have a reliable OS that works and receives regular updates every few years. Of course, everyone's needs are different, and sometimes a little tweaking is needed. But more often than not this concern is raised by those who are aware of the Ubuntu release schedule, even when there really isn't cause for it. At least that's how I see it, I'm very fond of the "don't fix it if it's not broken" philosophy.
That would be a great addition indeed, maybe for ZorinOS 18? 
In the meantime, you can install it yourself pretty easily:
Still having issues installing Z17 Beta on hardware, not sure what's going on there...