I think you're probably mistaken about the mic. If your car doesn't have Bluetooth, it won't have a mic, it won't have the HFT unit, it won't have any wiring in place. There's probably a unique imid to allow for Bluetooth etc. I doubt you can just drop in a new head unit and hope it'll work. I imagine you'd have to do a lot more and pull your car to pieces if you want to install the factory system.
To be honest, I think you are wrong.
It makes no sense creating different i-mid's + you know its possible to retrofit the navigation unit right? You won't get a completely new i-mid unit with it...
The i-Mid itself just displays information sent to it from the radio and ecu.
Theres a wiring harness connected to the i-Mid and if a signal is lost - it will just not display that information.
Adding a aftermarket radio proves this as the i-Mid functions still works after removal of the oem radio - but it's not showing any song/radio information.
Which leads me to believe adding the oem radio with Bluetooth function, that setting will be enabled in the i-Mid as the radio is now sending information on that wire.
About the mic - I will tear it down to check later. Wiring might be in Place with a connector but no mic. We shall see. If that is the case, the mic shouldn't be so expensive.
It's not the first time wiring is already in place as it's easier to build cars this way.
In Toyotas this is true but I'm not sure about the new Hondas.