For the top picture, absolutely not. The brake levers and bars are stock for 1973, the bars are shaped differently, the levers are mounted halfway down the bars, not as high as on the top picture, and I have stage III osteoarthritis in both hands... but I could never have gotten enough leverage to apply the brakes from the top hand position, even in 1973.
The brake extension levers in the lower picture, yeah, that would be workable. But the top of the bars is no longer really high enough. I do get what you're saying about leverage.
In my normal riding position on this bike, either in 1974 or today, my hands are nowhere near either the shifters or the brakes. If I think I *might* have to brake, I have one hand on the drops, the other on the top, so I can go either way depending on what happens. And this is for riding in intense city traffic, with people and cars flying at me from every possible direction. Just the ride I grew up on and what I'm used to.
This is the part that worries me, yeah. For hard cornering, I would always be on the drops anyway, of course-- that's second nature-- but I have no idea how it would handle. Also, I keep asking myself for
wolfcut, "Would the leverage and handling really be worse with extenders than replacing the bars with something straighter and some rise to it?" I think the answer, unfortunately, is yes.
And crap, I'm hijacking this thread! Just what I didn't want to do!