Gav, I'm not disagreeing with you at all. Just in the past I've found customers welding willy-nilly all over ROPS structures. Welding brackets for hand-held fire extinguishers or automatic suppression systems on the support legs was always a favourite, welding brackets for site numbers, beacons, Dispatch system/radio antennae, etc, etc, were others.
I haven't been up on top of an 11 for a few years now but on our current 9T's and 10T's there are 4 round bosses about 75mm diameter and a about 50mm high with something like an M16 thread in them welded to the roof of both the cab and the ROPS in a pattern about 750mm square. You can make a 6mm thick base plate to bolt on to those bosses then weld whatever on to that plate that you like. We shouted long and loud about it, it looks like Cat finally listened.
If I get close to one of our tractors in the coming week I'll hop up and take some photos of the roof.