I was directly involved in a discussion about these rails at the doors (I guess it was 2019 or 2020, I do not know exactly) with Ineos.
My statement was: "If someone would consider that as useful, I would have seen it once in the 15 years I'm active in the 4x4 community on some occasion, at fairs, while traveling or any other event. Someone would have mounted such rails, which are so common and well known and which you often find (but not on side doors). If anyone would have seen any sense in that. But I have never seen a single car with rails on the doors.
When you go camping with a car of that size the front doors are the ones which are opened and closed many times to get stuff out and in the car. It makes no sense to attach something there, while stationary. While driving it is not legal to attach things there on public roads in many countries. While on tracks or doing serious offroading I consider the rails just as collectors of dirt, branches (which lead to scratches), etc.
In case you're standing inclined on a slope having load attached to the doors, that will make them not managable. If you ever needed to open a side door (especially these heavy and ultra-robust doors of the IG) while standing inclined on a slope, you know how heavy and difficult it will become to open the door or to hold it open while you crawl out (Attention: getting hit or squeezed by such a heavy door can end up in a very bad experience). If you put additional weight on it, lets say a 6 kg fluid container...have fun opening the door and trying that it not crashes back into into the car (or you)."
I would be interested if anybody who considers these rails as useful has mounted such rails on his 4x4s in the past? If not, why are these rails are so welcome now? It doesn't take much of a genius to develop such an idea on my own. Especialy for people who tend to modify an optimze their 4x4. However, I never came across this, not while camping not while driving a trophy.
These rails just make the production more complex and expensive, while the usefullnes is in question. If it would have been clear to everyone what these are for, we wouldn't see some discussions about these rails here. I think it will end up like many other camping stuff. You go into the shop, buy this and that, all that fancy stuff but over time, with increasing experience, you filter out what is essential, what is practical and what was just a waste of time and money.
These rails are the pure idea of someone who like the car to look like a All-Time-Ready-Trophy car without any experience in camping, as this person prefers to sleep in his own hotel. However, my thoughts on this, of course, had no weight, as I'm not the sponsor of the Grenadier and the guy seems to be right, as these rails seem to attract a lot of people.
Actually I read the German Camel Trophy book by Nick Dimbleby, Andreas Berger and Volker Lapp which covers the complete Camel Trophy history very deep in detail. All the cars and their equipment are shown and discussed. No door rails... I know Volker personally, I'll ask him what he thinks about the rails.
AWo