IGH's are not all that rugged. Most have a published requirement for a minimum ratio between the chainring and cog, that translates into an approximate torque limit. I love my old Sturmey Archer AW hubs, but I'm not sure I'd recommend one for the aforementioned use case.
Seeing how as I regularly managed to break the drive cross in my 3-speed SA hub just by pushing the thing real hard under pedal power alone - this is 40 years ago - I don't think they're particularly strong. I fixed my bike by myself so all this cost me was a new drive cross but still, it shouldn't break in the first place.
The cross is made of a fairly hard type of steel. They knew how to make that 40 years ago so I don't think there is any noticeable difference. If anything I suspect the older gear hubs were built stronger than the current ones.
