Just eliminate the player limit altogether. I've seen plenty of videos of large mobs of men running a guy's pockets. There's no 'realistic limit' for an amount of people to rob a guy — a victim is a victim and will be treated as such in the hood. Keep the rest of the rule change if you like.
My logic is that there's no reason to create an arbitrary restriction that opens players up for punishment and wastes admin time when the typical reward for a robbery is so pitifully low anyhow. Long gone are the days when you'd pocket $5,000 from hitting a lick. Now you either know beforehand that they have guns or drugs, or you get a pittance. Why wrap that up in more red tape?
Not true, of course. Countless number of scenarios that would call for a robbery by more than 2 people lol. This is just throwing the baby out with the bathwater, totally arbitrary rule.
I'd wager that, these phantom 'robbery squads' aside, the people affected by this rule change will be players committing a robbery in a SMALL GROUP of more than two people finding their roleplay put on pause by an admin telling them it's unreasonable to roleplay a robbery with X amount of players. Even Bonnie and Clyde had backup. Who had the bright idea that this was a good change?