I think your analyisis is missing something more fundamental - men's fundamental biological advantage is higher risk-tolerance, physical strength was associated with surviving physical risk to a degree that it justified the higher calorie expanditure powerful muscles require. Even with a lot of mechanisation of heavy lifting, men would still be more willing to do anything dangerous because a kin group can afford to lose a few men. It seems less that modern society has a reduced need for physical strength than that it has a reduced need for individuals to take on personal risk - and in fact, the way that risk is largely spread out through society in the form of the social safety net, one might say it has not just a reduced need but a reduced tolerance for risky behaviour. Tough times for men indeed. The instinct to take risks for admiration from our social sphere runs very deep, and there are only so many intellectual or financial risks worth taking.
Nobody has ever wanted to overload a cargo ship until it sinks but it seems like in the past ~10-15yr the idea of worthwhile risks even existing have become demonized except in the most abstract settings (math, finance, etc).
In 1980 the guy that fixed a radio antenna in a blizzard because "what good is fall protection if I don't use it" got told he did a good job. Today he would be chewed out for taking unnecessary risks.
Even in finance, risk has become so socialised (thinking in particular of the wall street bailouts) that it's hard for an individual to take on a larger share of the risk for a larger reward even when he honestly wants to do so.
