I browsed back into this discussion and thought I would add how we are dealing with it.

If you take over managing your music on the iPhone manually, you can still sync calendars etc. automatically. Because I have way more music than the iPhone can take, it's not too inconvenient. That way, I keep the ringtones deleted from iTunes (after the first copy over, obviously) but still on the iPhone.

It's not perfect but I do get to use RB perfectly and my girlfriend still gets her phone to sing the Homer SMRT song whenever I call her iPhone.