Even with a barrel nut or barloc setup, you'll have to loosen the action screws or remove the action from the stock during a barrel change anyways because the front action screw on an AE is in the recoil lug and not in the action. Things are going to move around if you loosen the barrel without loosening the action screws first as the action and rear action screw will no longer be attached to the recoil lug and front action screw. It's not like a Remington where both action screws go into the receiver.
Also, with the front action screw being in the recoil lug, proper barrel torque is going to be important to keep the recoil lug securely sandwiched in place to keep things from moving around under recoil.
While I sold them both a while ago, both my AE Mk3's were within the normal AI dimensional specs for prefits, so barrels were easy to find. Some AEs have a bit more dimensional variation from the recoil lug face to bolt face than AW/AT/ATX/AXMC's because of additional tolerance stacking with the recoil lug.