REALISTIC LIVE BLADE (TM) testing maketh lifespan of Tori very short... Uke will run out of training partner very quickly.
Having say that, I am curious, how does the Kenjutsu students of old train in the old days before shinai and the armour was invented? Serious question.
Seriously, from what I've read, they used bokuto (bokken). Some ryu also used an older version of the kendo shinai called fukuro shinai or hikihada (toad skin) shinai.
See the movie "The Last Samurai" for details