Planes generally can't pull more Gs than the humans inside without needing to go through an extensive maintenance process.
Even then, as has been said countless times in this thread, high-G maneuvers don't do shit against modern missile threats. They might be useful for dogfighting with guns, but given the range and accuracy of modern missiles, combined with proximity fuzes, it simply doesn't accomplish much.
Against a weaker enemy, you'll never have the need to pull Gs in the first place. Against an equal or stronger enemy, it won't do a damn bit of difference anyway.
Even then, as has been said countless times in this thread, high-G maneuvers don't do shit against modern missile threats. They might be useful for dogfighting with guns, but given the range and accuracy of modern missiles, combined with proximity fuzes, it simply doesn't accomplish much.
Against a weaker enemy, you'll never have the need to pull Gs in the first place. Against an equal or stronger enemy, it won't do a damn bit of difference anyway.