[jp10]

IMO body armor would best be represented if the game calculated 'Kills' as 'wounded' and 'killed'. A typical ratio of 66% WIA and 33% KIA during an action is a historical standard. Urban/Mountain combat is more 50/50 while actions by geographically isolated or forces with poor medical service is 40/60.
Body armor would merely increase the % of 'kills' just being wounded and victory points being modified for that unit. Infantry (foot) units would lose a movement point to reflect the lessened mobility and increased fatigue induced by body armor.