You could add some rng into the mix and increase it for those that camp. Make it so at any given time you have a 1/100-1/1000 chance per second for your Jihad to trigger. Then you would want to stay somewhat near people because if you weren't and you didn't surpass the kill threshold, you're just going to detonate and then you're out.
You could make it so that it had tiers (assuming GMod is capable of location tracking like this). You could have it so that if a player doesn't move at all, his chances go up drastically to trigger (2x-10x or something). A player who does move, but doesn't move within a ~5m area over a period of time like <5 seconds has his chances go up by 1.5x-5x, and a player who does move but doesn't move further than 15m over a period of time greater than the previous, has their chances go up by 1.25x-2.5x. These are all just example numbers that would probably need some work to balance.
You'd be encouraged to stay moving, and one of the best ways to keep moving would be to continue to target people. It would give a default disadvantage from trying to isolate yourself. This is similar to bomb rush where if you stay hidden from others, you're most likely going to get a bomb even if you're not given one, so if you want any luck at winning you'd have to stay within reaching distance.
Idk tired and spitballing here.