Simple and sophisticated answers
Simple answer:
#1: Keep a count with high betting efficiency
#2: Keep an ace-neutral count with high playing efficiency
#3: Keep an ace side count (for single deck game, this person may also keep a side count of 7 and a side count of 5-6 differential)
#4: Keep an insurance count
Sophisticated answer:
Randomize the bet size of these four people, but make the total bet size highly correlated with the true count (each counter needs a big bet spread in order to achieve this). Also, for each hand, use only one person to count and use the other people to talk, act, and distress the pit managers. At the end of each hand, the counting player will pass the running count onto another player.