Custom field rendering in modern list views

Generic scripting is powerful, but it tends to be fragile - customizations tend to break when we change our default UI.  Just ask our support team!  So we want to focus more of our efforts around making specific scenarios work in a robust, guaranteed way.  We want to build developer contracts that ensure certain scenarios (and scenario patterns) will work consistently as we make continuous updates to the service.  

All that said, we have definitely not precluded giving developers the ability to do generic JSLink/CustomAction scripting on our pages - but we're trying to figure out how far we can get without doing that.