The RJ/E3 nav does the same job as older ME aircraft navs once did, such as on the VC10 and C130K. Certainly with the E3, it's virtually the same flight deck as the original aircraft, hence the need for a flight engineer as well. I understand that the upgrade will remove the nav with a Gucci FMS and rumour has it that this will not be complete until 2029.
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.
As for NCO aircrew doing the Aero Systems Course, this is not new. Can't remember when the first student completed the course but I think it's been at least 10 - 15 years.