Well, yeah. But we've been down this road before.
That time it was about conflicting windows messages, but you told me to switch to mc commands. And that has been working perfectly since then (it may have been using 14 and 15 together, I can't remember - it's been a long time). For my system I am totally dependant on two different versions so I can call mc16.exe and mc17.exe commands seperatly. One for radio and one for regular music. I can't use the same zones for music and radio because my son, my daughter and my wife gets insane (and I get violent towards inanimate objects...) when a quick listening to the news wipes out the playlist they were listening to, so they have to be separated. And having 22 zones on one version isn't good either (with one zone each for radio and music for my 11 physical zones) because that makes the NetRemote control that we all use on HTC HD2 Windows Mobile 6.5 phones very messy. So two different versions is a necessity.
Couldn't that be an "advanced" choice, to close or not close 16? As long as it's not used for video I don't think anything can be messed up by having those two versions running side by side, right?
Edit: Oh, and if somebody thinks my system is unnecessary complex they should have heard the radio signals we get out here in the sticks... But this has worked 24/7 for years without any problems until the main Norwegian state owned broadcasting station NRK went from WMA to AAC on their high quality streaming and for some ¤¤¤¤ed up reason chose a version with a non standard gain control system...