>>28511171
>full-feature aftermarket solutions seem unlikely
but they exist already so all the shit you're talking about is bunk
i know for example scosche makes a kit that replaces the hvac controls in mopars with their own screens leaving the dashboard screen open for any old random chinese head unit.
i'd personally prefer a button and knob based replacement but it really isn't the kind of impossible task you're making it out to be.