KIX immigration/security lines at that time of day are not that bad....especailly if you get moving off of your flight and get to immigration ahead of the rest of the flight. After 9+ connections there getting back through security hasn't been a problem at any time of the day.

If you decide to hit the shops and/or restaurants you still need to clear into Japan as the main terminal complex is not airside. If you are changing airlines and do not have your outbound boarding pass when you arrive, check to see when you can check back in for your next flight as you will need the boarding pass to clear security and into the international terminal.