I think it's possible(with some testing) to rig the weapon to arm bones or different bones on the skeleton, so in idle it moves a little, but if you perform actions the flail chain responds. I don''t think the weapon itself can be rigged, but a custom piece of apparel can be equipped with a script if you equip the weapon. The weapon itself has to be replaced with an invisible one in due course but that's not hard. May ruin the immersion a wee bit, but hey, if it works then it should be worth it. Better than a constantly flailing flail