Sticking my unqualified oar in...
I think the Mech Eng would be better for structural designing (Metallurgy, Stress, Etc) as that is where many pitfalls are found first. The Aerodynamics comes later - when you know how to build something to withstand forces for whatever reason - that is the way of Structural Design Development.
CAD is Okay - but still needs an experienced operator to drive it.
Systems-wise, again a developmental thing, that comes with knowledge and experience to avoid older errors and mistakes and to develop new atitudes and reasoning.
Go for the Mech - and keep your own design going in the background - keep thinking about it.
You never know? You might make it work better!
Best of Luck
Rigga