Hi Rohit,
Thanks for your email, and so sorry about the delay! It's been a rough couple weeks or months...
It'd be great to have you contribute. Breeze is, as you probably surmised, more of a numerics (~numpy/scipy) library than a machine learning (~scikits-learn) library. But that's not to say that we don't need help (we do!), or don't want machine learning capabilities. I mostly use Breeze for machine learning and NLP, so in general that's good to have.
Before I suggest anything concrete, what's your experience with Scala? What I suggest depends pretty strongly on that.
You might also look at mllib which is a proper machine learning library.
-- David