Rotating the torso without mouselock or first person getting in the way?

I have a tool that uses welds to animate the player's limbs. There's a certain ability I'd like to make that requires the player's torso to rotate 90 degrees - however if I'm playing in MouseLock or first person mode, the torso refuses to rotate. I can't anchor the torso because, due to the way I have the welds for my animation set up, that causes only the torso to rotate and not the arms.

tl;dr Is there any way I can rotate the torso without anchoring it, and not have it affected by Mouse Lock or first person mode?