Currently, CAS aircraft are weak and not very interesting, and have been the subject of much debate on a potential rework.
I have a simple suggestion - CAS should do bonus morale damage to units within a formation, equal to (CAS_Coefficient*Units Destroyed By CAS in Combat Phase/Element Class Size) * (100 / Element Morale). Effectively, CAS would deal extra Cohesion Damage to each element. Given the current ineffectiveness of CAS, I suspect that the CAS_coefficient would need to be set to some value like 5 or 10 to make CAS worth using, but that would be up to further testing. This is my reasoning for this suggestion:
A. It is simple to implement. It's almost the same calculation as Cohesion Damage, which is Element Class Size * Units Destroyed in Combat Phase * (100 / Element Morale).
B. It gives CAS a radically distinct capability from ground units. At present, CAS is more or less "heavy artillery but it can be shot down," which is not very interesting.
C. It keeps CAS firmly as a support asset and doesn't trivialize the ground unit types. The direct damage would still be pathetic and CAS more logistically burdensome than ground units. Heavy Artillery would still be superior at hitting rear echelons from a safe position.
D. In terms of roleplay, it would make CAS extremely useful at assisting breakthrough through damaging enemy morale, but not very effective against well fortified units. Now we can simulate blitzkrieg.
There are possible elaborations upon this suggestion, such as making the morale debuff tracked separately from normal morale damage and fade more rapidly to model suppression, or to have friendly anti-air damage dealt directly reduce morale damage taken. However, the simplest suggestion possible is more likely to be implemented and to be worth Steve's time, given the relatively marginal important of CAS and ground combat in general.