DirtyDan This is what I've done the last hour. T-Mobile here and RCS quit for me a month ago.
I used to be on 262366063; as I said, RCS quit. I re-installed this version, and it said RCS isn't available on the device.
Downloaded 242499063 from Aurora, RCS said connected, though not working. Updated the app via Aurora, and RCS still said connected.
Just for fun, I tried this method, obviously uninstalling Messages first and doing everything. Installing from Play Store, RCS says 'connecting...', rebooted the phone, RCS is still connecting.
I will now keep things as is (even though I don't like Services having network perms), wait for the GOS Stable update to come out, and see if anything changes (despite there being no mention of RCS in the changelog). If not, I'll uninstall, re-install v2424, and wait a few more days...
When I was on v262366063 and RCS was functioning, the only permission Play Services had was phone. No network needed.
This is tiresome.