you seem tech savvy, ever thought about a VoIP System? I have VoIP phones in each room and can force them to auto-answer on a specific extension (speakerphone unless someone picks up a handset).. i ring all mine up with auto-answer and drop em into a conference room for a quazi-paging/pa system.. I dont have the remote needs you do, but its proven great when someone is sick.. my office desk phone will ring once then I hear my wife ask for another box of tissues, she just hit a contact in her iphone and never got up out of bed..
each room has a phone and I have a line in the house for each person thats rang at the same time as the cell.. so if you cant find your cell or the battery is dead you can just get up and answer.. or if you want to see who's calling without finding your phone you can lookup from your chair and see.. I built it because I am in a mobile dead zone and no carrier has a good signal.. now I have micro-cells for both sprint & att but the voip system proven too useful to retire.. we use almost no mins but its great for hearing incoming calls, checking caller-id quick and easy, and of course internal comms
then you wouldn't be dependent on the 2-way audio features and could use whatever video system you wanted.. the latency would also be as good as any phone system, at least the audio.