If you were to have a dream team…

Well, I guess weakening the disguise ability makes some sense…

Aegislash I like mainly for its Ability, Stance Change. It starts the battle in Shield Forme, with really high Def. and Sp. Def., but if you use an attack, it switchs to Sword Forme, swapping its Attack for its Defense and its Sp. Attack for its Sp. Defense. Then if you use King's Shield (signature move similar to Protect, but penalizes direct contact with a reduction to Attack), it switches back to Shield Forme, once again becoming a bulwark of Def. and Sp. Def.

This works really well because Aegislash is so slow that its attack comes AFTER the opponent, meaning that their attack does very little against the high defensive stats, but King's Shield is a priority move, so it can switch back to Shield Forme without exposing itself!

That way, Aegislash effectively has 200 Attack, Sp. Attack, Defense, and Sp. Defense (though in actuality it just switches the stat value back and forth).