[PlasmaKrab]

IMHO you should think more in terms of force size. The OPFOR in this scenario gets one tank platoon, one mech platoon and complete infantry support units first thing, then a reduced tank co (9 tanks) with 2 mech plts as reinforcements.
In the various avatars of this scenario I have patched up in the past (good materials test range even if the morale is buggy) I tried to give the initial defense troops lower-end tanks and keep the top-notch versions for the reinforcements. E.g. you could use Leo2A4s and Leo1A5s (or AMX30B2s), facing only M1A1s which shouldn't be any more expensive than the Leo2s.