Depending on the level of the game, the effects of suppression can be abstracted into the general degradation of unit effectiveness. In most games, when we kill a unit/stand/figure, are we really killing it or just making it combat ineffective? Arguably, suppression is just a temporary (hopefully, depending on your outlook) manifestation of this.
I would argue that suppression is best handled as an effect of the weapon system in concert with the morale/training/leadership of the target unit/stand/figure. I would say that “trading” casualties for suppression is best handled as an intersection of mission motivation as expressed in Stargrunt II and morale/training/leadership. Also, it should be tested for rather than a conscious decision of the player. But then, I like friction in games.