Imagine this:
Every recruit has exactly 3 perks – one physique trait (strong, asthmatic, …), one moral trait (brave, disloyal, …) and one special trait (f.e. spartan, cocky, or some new traits).
Physique trait should be visible to you when hiring (its plain dumb when you hire expensive clubfooted swordmaster…), however other two traits will be hidden till recruit`s first battle.