Durability of standard ML (W163) alloy wheels?

As there are evidently quite a few past and present ML owners on here, I thought I'd ask, as this is my favourite forum and bunch of people 

Situation is this:

I have a ML430 here which, between everything else, I need to prepare in order to be able to handle rutted and potholed gravel roads at speeds of minimum 60mph.

In regards wheels and tyres, first thoughts were to with spacer/adapters, change to G-wagen steel wheels and 235/85-16 or 265/75-16 tyres. The problem with this is that the spacers would need to be roughly 75mm thick and in steel (to handle steel wheel bolt torque and for strength and durability) and that seemingly no-one is willing to produce such items.

The 75mm is approximate at this stage and is needed for the 16 inch G-wagen wheels to clear the big brakes (same as 500/55) of the 430.

Once upon a time, more than 20 years ago to be precise, I used to be a fitter and turner. So I COULD go and source a lathe and mill and just make them myself.

But then also thought/wondered if the standard ML alloy wheels may be able to stand up to punishment if I went to for example a 265/65-17?

The real question here is this: Of all you past and present ML owners, did you ever suffer a broken/cracked/bent/buckled (genuine MB) 17-inch alloy wheel? Or are they super tough?

Would really appreciate any input and/or thoughts or suggestions.