Reply to Idea's for S4 & SL 25 MKII Mappings?

I just recently purchased a Novation SL Mk-II 25 Midi keyboard. I have Jack OSX running to sync the audio from my Kontrol S4 Traktor 2 Deck's A, B, C and D into Ableton live 8 each in their respective channels, then have the master in Ableton routed back into Traktor or my S4 controller and out the mains in the back. There's a detailed explaination of how to set this up yourself here: http://www.youtube.com/watch?v=4xzldehIsCE
and
http://www.youtube.com/watch?v=ShO7FbOuSrQ

It's working great so far and I'm loving the midi-sync from Traktor to Ableton so the keyboard's arpegiators are in beat with my S4 decks.

Now faced with a world of new options, my question is I'm fairly new to Ableton and midi-keyboards, so what are some cool VSTi's to use, or how would you integrate the two? I was believeing of using the keyboard for little loops of simple melodies during particular songs, or using it as a crazy effects processor for each of the decks A-D (However I'm unfamiliar with good effect vsti's on ableton). I could also set it up as a sampler, applying different samples to each of the keys. I would like to keep the keyboard for control of ableton since the S4 does a perfect job of controlling Traktor completly.

I'm a bit over whelmed, but that's a good thing If anyone has experience with Traktor-Ableton and/or midi keyboards, toss me some of your ideas or templates.