The scale of Aggression mentioned in the Alpha rules includes Berserk at the top, but it omits the equivalent at the other end: Suppression.
This follows from Pinned and is an even less happy state. Mechanically it works identically, being another step along the Aggression continuum. However, because Pinned can be removed in a single short action it is a very temporary effect. This is a good modelling of real reactions to enemy fire: targets are only impressed for very slightly longer than you are actually shooting at them. It takes more effort to persuade them to keep their heads down longer.
Because Pinned isn’t long-term it makes it hard to stop enemy attacks and makes Breaking Away a problem unless you have friends nearby to help out and shoot the enemy while you bug out. I rather like the fact that this encourages teamwork among your forces, but it needs to be possible to discourage attackers more thoroughly.
If you’re interested, try using Suppressed as the next step down from Pinned. As you’re only allowed to Get Mean once per turn this makes it work very differently in practice.
Give Suppressed models a -2 in melee and otherwise treat it as Pinned. It’s a tiny change in rules, but adds rather more to the tactics.
Let me know how you get on 🙂