Multiclassing is a fairly lukewarm set of mechanical options, so utilizing it as a solution to something that could just as easily be baked in to a class is pretty unappealing. I guess I could see it for the manaball, but whipping shurikens is inherently a monky option.Multiclass.
Maybe a paragon path could open up some options for channeling ki into pure energy.
And again, I entreat WotC to keep the ki power source in lieu of the psionic power source, rather than vice versa.