I've got a similar idea but a little bit more involved...
I've got hold of a second Navara sports bar and plan to take the bracing legs off each of them and mount the second one where the legs would usually be. Then with the help of a boiler maker mate, tig up an aluminium lockable storage cage that sits above the tonnau cover with a gull wing door each side. Plan is to look as 'standard' as it can get it.
Guido