* Coolant leaks: This will lead to overheating, potentially causing catastrophic engine damage.
* Engine damage from overheating: Overheating can warp the engine block, crack the head, and ruin internal components. This is far more expensive than replacing a freeze plug.
* Loss of engine pressure: This can affect lubrication and performance.
While you *might* be able to drive a short distance very carefully, it's extremely risky. Do not attempt to drive the Jeep without addressing the missing freeze plug immediately. Get it repaired by a mechanic as soon as possible. Continuing to drive it could cost you thousands in repairs.