In my opinion kakashi would win hands down.

On round one there would be no sharingan/ms, and no sacred gear. Kakashi would win because he was great before the sharingan.

Round two, justsu is allowed, 3-tomoe sharingan and bosted gearallowed. Kakashi would still win because he would be able to predict his attacks.

Round 3, balance breaker and mangekyo sharingan is allowed. Kakashi would probably use kamui so that would be over. And furthermore Kakashi would stomp issei because Kakashi is Kakashi and he is just better at fighting. The only thing that could give issei a chance is juggernaut drive or poking rias in the boobs.

So in my opinion Kakashi Hatake would stomp issei. Let me know what you guys think.