Biggus
perhaps a wee bit more knowledge needed.
just as in the case of the Air Engineer (also required on E-3D and RJ)
The E3D does indeed have an Air Engineer, whilst the RJ most certainly doesn't. They both do have Navs, so in this you are correct.
Party Animal
Not sure why our brand new RJ's didn't go down that route from day one but I suspect that just like everything else - it's all about the money.
One of the beauties or the UK RJ, or so I'm led to believe, is that it is part of the upgrade programme as with the US RJ. There is currently no upgrade baseline that has a front end without the Nav. Perhaps in the future, but not now. Nothing whatsoever to do with money.