I think it would look smoking but have some concerns about running over players, hitting snipers and bad road condition roll-overs.
If you could make strict rules for the vehicle it may work out.
-Have a visible track (road) that the Jeep must drive on and cannot be driven anywhere else.
-No people are allowed to be on the road/track except to cross and only when the Jeep is visibly far away.
-Jeep gun should be allowed to shoot over 400fps since it cannot move away from track/road.
- put a throttle limiter on the Jeep to set acceleration to a slow speed and limit speed to max 25-30km/hr.
Beyond that great idea and go for it.
P.S. Oh yeah, Jeep TJ's are pricey machines, I'd suggest you get a beater Suzuki sidekick or something that won't be considered a classic or appreciate in value.