Sounds like mod material to me. Also, hardcoe mode shouldn't have anything to do with strength and numbers of enemies.
Agreed on the second part
Numbers of enemies is an extremely bad idea, as it adds strain to the system you may now not be able to handle. And the difficulty slider takes care of the, well, difficulty. As for the first part, yes, increasing strength is indeed mod material if you want to go beyond the difficulty scalar. But no, hardcoe mode should be built in to allow also console players some added depth to the game.
But personally, I'd prefer having a whole bunch of difficulty sliders where I could adjust all kinds of difficulties and skip "hardcoe mode" altogether. But you can't set them so that the average goes below 50%. If someone hate the concept of nutrition and rest, dial down the survival difficulty and increase something else to match, like leveling difficulty, player vs foe toughness ratio, foe respawn timers etc. Setting survival to 0% forces you to set the three others to 66-67%, not a *big* increase.
This is role playing, it's playing a predefined system of rules. In dice games if us players think something needs to be adjusted we ask the GM. Here, the computer is the GM,so we should be able to adjust but being forced to stay "within reason".
Also feel free to add your vote for or against here, which is a dec. 2010 thread:
http://www.gamesas.com/index.php?showtopic=1148533&st=