As plawolf said I don't think mines will be a threat from Japan. In fact not much of Japanese military can be a threat.
IMO the biggest threat from Japan would be if they open their territory completely to US military for missile and airforce basing, basically an unsinkable aircraft carrier that can trade blows with coastal Chinese cities. That will of course guarantee the complete destruction of Japanese infrastructure and economies so I imagine it would only be a last resort for Japanese regime, it is still a scenario Chinese planners need to take into account.
Exactly. This is why China needs a Japan bomber not some ridiculous CONUS bomber.