In the attack, since the reaction turns really dont count - try using reinforcement arrival for the later waves. Reinforcements are much more controllable.
E.g use to time it so the armour arrives on the line as the leg grunts engage, or to make human wave #2 step off 2 turns later, #3 2 turns after that etc.
Just deploy them on the start line, but set to arrive as reinforcements a few turns after game start. That gives you better control of the timing (it may mystify a human who tries to play the scenario as the normally AI side - however as a designer you may well
want to limit his options
!
Cheers
Andy