Is your feature request related to a problem? Please describe.
While there are light sources that one can hand-hold, they can be placed on to blocks, which can create awkwardness when a player isn't super-careful with their buttons.

Describe the solution you'd like
An entity light source, like a form of a torch. This torch cannot be placed anywhere that is not a storage block, and the action button can actually switch the light from on to off, if the player builds a torch with such mechanism. So there are at lest 2 carryable light sources, one with and one without the light switch, and it is up to user choice as to which one they want to have.

Describe alternatives you've considered
Maybe an attachable light source in a helmet? One that can be turned on/off with a set key.

You're asking features that'd best fit a content mod rather than a client mod.
Such content mod could use this mod's API though.