I had been poking around Crutchfield off and on for a while now. I found head units that would maintain compatibility with Bose system and steering wheel controls. IIRC, every one of them I saw specifically mentioned the loss of RSE control functions. I hope to upgrade in the next six months, in order to gain bluetooth, Android Auto and hands-free calling. If I am able to keep steering wheel controls and my Bose, I don't think I will not giving up rear seat functions.
I have had great experience with Crutchfield. If you consult with them as you are deciding what to order, they will make sure you get something that works. That may not include rear seat entertainment control capabilities if the new equipment won't allow it to happen, but they will get you something that works, really good written instructions specific to your vehicle. They will even walk you through installation, if necessary. That is a lot of free help that other suppliers can't or won't give you.