Has it ever been stated specifically that the breaking point (Bakusai...) 
 can't be done with a projectile?

No, it has not. You can adapt the Bakusai Tenketsu any old way you want. In
fact, there's precedent; in TMTC/TPOH, Ryo Muhoshin develops the Bakusai
Tensatsu and the long-distance breaking point, both of which are similar to
your idea. 

-Mercutio
"A plague 'a both your houses!"