What's the easiest/least expensive way to bring everything else together, and have bluetooth capability so that both riders can use their phones as well as the other features without running dual headsets into both my helmet, and my wife's?
You rip out all the add on bits that are left over, get a pair of SMH10 Bluetooth headsets for your helmets, and a SR10 interface to a CB radio if you think you absolutely must have it.
Unless you are putting about below 35 mph the bike's stereo is useless. Bluetooth to your phone will give you better music than you can get from any BMW stereo. Want Sirius/XM? just install the app on your phone and listen. If you really want to listen to FM radio you can use the FM tuner in your headset.
The BMW stock radio is designed for use with their wired headset system if you wanted to hear the music, you can buy a $600 wired unit to replace what is missing but you then can not have Bluetooth for the helmets only wires. Add $295 for the Bluetooth to the phone that will only let you answer calls.
If you want the best intercom system with bike controlled music, then that is wired headsets and about $800 to $1000 in parts if you install it all yourself. If you want Bluetooth you really need to abandon what is on the bike and go pretty much as a complete separate setup, Fix the bike stereo so you have tunes to listen to while you wash it.
I just went down this road and spent a lot of money on trying to make the on bike system work the way I wanted. It's all in a pile on my floor waiting to go on ebay, and I have a pair of SMH10's on the way with a SR10 for interface to my Ham Radio two way. All of it fits in the tank bag, I can listen to XM,FM,all of my music collection on the phone, Pandora, etc... the wife can listen to her own music or chat with her friends on the phone, or as she prefers, talk to me so I cant hear my own music.
Bluetooth does not let you listen to music and intercom at the same time, so keep that in mind. Only a wired system will mix the music in with the intercom.
But the SMH10 will let me make a phone call completely with my voice, I can also control the music by play/pause/etc by voice as well (I use the iphone that has voice control)
So you actually need to make some decisions, is having music from the bike in your helmet very important? if so then your only choice is wired. Look at Autocom SPA and the Autocom Bluetooth phone adapter to hook in your phone, also you need to get the autocom radio adapter to hook to the CB, then another autocom adapter to hook the stock stereo speaker outputs into the autocom. You also will want to get a set of coiled headset extensions at $50.00 each.
I found it a lot easier and cheaper to just abandon everything on the bike, and I end up with a better system that does more.