Can't add anything to the commisioning side, but they are looking for AT's on RJ currently. I've looked into AT recently, the E3D AT slots are booked up for the next 12-18 months, but you can still register your interest.
My suggestion would be to arrange a visit to Waddo (or where they respective fleets are boltholed atm) and spend a couple of days looking at the various roles AT's perform on the aircraft. Most poeple I've known that have gone down the AT route don't regret it. But it suits some folk and not others, like most things in life!
PM me if you want more information, and a steer to who you need to speak to on the E3D side of things.