No point really. If you're gonna do cool, you might as well do heat. That's a four hose pack with wiring to run the rear fan. Might as well go modern and do seperate controls for the rear stuff. The possibilities are endless. Just a matter of how much work you want to do.
My wife's '99 Suburban had rear air but the heater never worked so well. Her '09 Traverse has rear air with seperate controls. Funny thing is, put the kids in her car and you can't get the rear A/C on fast enough. Put them in my '98 Crew Cab, with slow to cool, no rear air and they don't complain at all about the heat. Eventually it gets cool.
