An Adult Swim for Nickelodeon...

Personally, I always thought the world would be better off without these cartoons.

Hmm, so far, Nickelodeon seems to hold to its current format with no sign of diversifying, which would be a form of brand dilution. However, if Nick did consider a mature programming block, the question arises as to which production studios to tap for content. Of course, if they could swing a series or two in-house, that'd be ideal, but that won't be enough to fill a devoted program block. Going down your list:

* Ren And Stimpy by John K Studios. Not likely. This series is dated, and John Kricfalusi is somewhat of a pariah in the industry. I strongly doubt Nickelodeon wants anything from that studio.

* Beavis And Butthead by Judgemental Films. Another dated series. Mike Judge currently has a cash cow series with King Of The Hill. BAB was Mike's starter series, and it's almost an old shame of his. Pretty sure Judgemental Films will let this title die off in obscurity.

* Daria by MTV Studios. An in-house property for MTV, they're not going to let a rival broadcaster touch their stuff cheaply. Sure, more airplay of one of their productions would be a good thing, but MTV will want to be the broadcaster rather than (ugh) Nickelodeon. So, Daria is basically, "It's my toy; you can't have it! Nyeh!"

* The Brothers Grunt by MTV Studios. Not happening for the exact same reason as Daria.

Seriously, if Nickelodeon wants to broaden its content, I'd take a clue from Toonami and screen some anime from gekiga, iyashikei, and sekaikei series, possibly josei as well. Nickelodeon really won't be comfortable with the riskier stuff like Ranma ½ or Kill La Kill. Perhaps Wolf Children, Usagi Drop or Girls Und Panzer would work. Those overseas studios are very creative and very productive, so filling a programming block with their content is a win-win for everyone.