I've been shortsighted about the "trap a target guard" objective. I can just alert that guard and have them chase me over the sabotaged trap. That's much more fun than waiting ^^
Though I should remove the bonus objective "no alerts" for these missions, so I don't punish the player for such a devious tactic. Or keep the bonus objective for the patient players, in which case I should force the target guard to be near a trap so the game remains fair time-wise.