well you could always get *lucky* and win a cluster with maxed out loyalty. That`s about 2500 loyalty after battle penalty.
But of course unless you and a friend are both foolish enough to planet transfer, you`re gonna have to rely on luck and maybe heavy duty stalking.
Of course starting a campaign of historia spamming on someone who can`t dig who you know maxed out their loyalty is an option too. Then all you gotta do is be there when he comes out of dp or vm and take his planets. it`s the only way you`ll win planets from an empire that can explore besides waiting for em to go inactive. Trick is finding someone who`s actually done this. Tax empires like I described are mighty hard to find these days on slower servers. ^_^