I think the question should be asked of those who plan to explore the limits of legailty how they would deal with an engine failure.
Take the Pennines example of being able to see (but not reach) a distant peak, with maybe a 500ft (or less) cloudbase in the surrounds of it, the terrain avilable to land in being undulating etc?
Is it a question of Dirty Harry and 'Do you feel lucky punk?"
It would be safer to fly 4,000ft VFR on top across the channel, than it would be to fly @ 2,400ft under the clouds for precisely the "engine out" scenario imho. That is, of course, if you can GARAUNTEE that the wx at your destination will have holes for you to descend through and you aren't going to find yourself descending through cloud that is actually to the ground. Which, of course, you can't ever really garauntee no matter how unlikely a scenario it is.
So banning, non IMC from flying on top, does sounds like the safer thing to do, in my limited tyro inexperienced opinion.