I think it would pair really well with other first person rendering mods if the chracter's hand wolud follow the direction of the camera
(for example if you're holding a torch and look down, your hand goes down as well, which solves the issue of poor visibility)

my ideas of settings for this config would be like:

Players affected: all players / only self
items affected: config items (different file) / hold up items (the same items as the hold up config)
Hold up angle (could maybe be the same as the other setting)
stop at degrees up (slider): makes the arm stop when looking above or bellow a certain setting of degrees
stop at degrees down (slider): makes the arm stop when looking above or bellow a certain setting of degrees

You mean the rotation lock setting?

You mean the rotation lock setting?

no (in my idea, the hand rotates in the y axis aka up and down)