A merge doesn't sound like a wonderful solution. Animated programming makes up a good part of Nick's legacy, so "Nicktoons" is evidently a part of that.
Maybe just dedicate a block on the main Nickelodeon channel for sports or something instead of Nicktoons.
"NickGaS"
Hmm...what a juvenile name. Can't imagine people missed it.
I personally like NickFit better - has more of a ring to it...and could cover general fitness as well as sports, which keep you fit. Healthy commercials would also run on this channel for a coherent schedule.