Well I don't think you're going to get a "lot of light" out of anything you replace that with. If you try to put high intensity lights in there, you are probably going to have a problem because the wires are not designed for a lot of current. You might get away with a bit of a higher wattage bulb but that won't give you much more. Also, remember that the cargo light is paired up with the high center mounted brake light, and depending on where you live, if you disable or remove that, it could give you legal problems.
I'd recommend a light bar if you are really looking for a lot of light.

 

Even tho the light bar dosnt give off a lot of light they looks AMAZING!!! I have on on my truck and love it and they just tap into your trailer wiring.

 

If you want a lot of light, get some off-road driving lights back there. If you don't, then either mount some reverse lights on the back, or a light bar/hitch light. The line of fire light bar looks to be pretty bright in reverse.

 

i saw a guy who mounted a hella light to his back bumper. you just wire in its own personal switch the same way you would add lights to your bull bar or behind the grill. its very bright too
i think this guy did something like what i was thinking about

https://dodgeforum.com/forum/v6-spec...more-pics.html