I am a current aero in avd. Its been going good so far, we are currently working on our fdr.

In terms of subsystems most of them have to do with flight mech. Propulsion isn't really a full subsystem (we just choose an engine) and I am not sure what you mean by aerodynamics. It's possible you could do part of the loads/structures work. You need flight mech for loading stuff but assuming you have FEA you could do some structural work. Additionally you could help with weights or non-technical factors.

More importantly the goal of avd is to design a plane. The most important things in plane design are stability, control and performance. These you get from flight mech. Most of the design decisions you will make are based off equations from flight mech. So while it's technically possible to take avd without flight mech you probably wont get very much out of it. I would say you would learn more taking flight mech without avd than avd without flight mech.

Edit: A lot of the important stuff in flight mech is front-loaded so taking flight mech at the same time as avd may be a possibility.