Not really. Actually it's a very good idea. It's uncontrollable, and is just as fast as Frieza's, so at the moment, Krillin is nerfed.
This idea would be fine with some tweaking: You can charge it up to a certain point, and how far you charged it determines the amount of disk the original splits into (1 at min, 5 at max). It's thrown, and then the user can press primary again to make it split, and each of the smaller disk will have a slight homing ability. NOTICE: I said slight homing ability. It can lock onto any enemies within sight (if somebody is behind a rock or building, they won't be found), and after the lock, that's it. It can be easily dodged with a teleport, and the small disk wont lock on again. Code-wise, it would be easy (or atleast possible), since they'd only have to combine properties of kakusan (splitting beam, for the.... splitting and slight homing ability), a beam attack (the detonation, so that the disk can split), and the kienzan (to do the job of instant killing).
Ofcourse, a simpiler solution to making kienzan better (so that it's actually useful, compared to Frieza's kienzan) would be to make it faster.