Creating a medic or an engineer for the editor works fine because we can choose a class but in a Zeus scenario the loadout only needs a medkit in the backpack to heal wounded soldiers and a toolkit to repair damaged vehicles and to defuse mines. You can also carry both and be a medic and an engineer at the same time and in Zeus scenarios with custom classes only these roles aren't needed because every player can grab a medkit/toolkit and be a medic/engineer (or both) without having to spawn as one of these classes.
Therefore it would be great to have an additional tab in Virtual Arsenal named "Special Abilities" or something like that with the following options:
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Medic
Engineer
Repair Specialist
Explosive Specialist