Not a fan of dangling mic cords from the roof etc, I know some like them up there but it’s not for me, also not 100% sure there is soace up there for the hidden unit either and I definitely don’t want to be running aeriel cable down A pillars etc. Also I don’t like the aerial on the roof, it gets a bit better reception but you have to remember to knock it down going into carparks and it’s more vulnerable to trees etc on bush tracks. Just overall works better for me with the unit behind the dash, and the aerial on the bar.
Will be interesting to see if there is some kind of channel up there, but it may just be the wiring harness laid out and wired up before the headliner goes in, in which case it wouldn’t be just a matter of feeding a cable through, it would be a much bigger job.