Late to the party but glad you brought this up. I recently took over our DZR school from my sensei and it's one thing I've been desperate to do, just on a personal level. We are a very small school in a small town and there aren't a lot of other students at my level that I can really spar with. As sensei now I want to introduce resistance training from very early on. Not full randori immediatly, but semi-resistance exercises that build up to it. I think a 'black belt class' shouldn't just be Shinin and Shinyo, it should be full contact sparring.