Describe your suggestion...

This would be configured in a similar way as the block tag but instead of if an entity is standing on a block, it's if an entity is holding a specified item. an example of how this could be used would be if you wanted an entity to have a quiver on it's back, only if its holding a bow.

Does another mod also do this?

Probably not

Does OptiFine do this?

No

This exists already in etf it is the item tag, you can also do this with the nbt tag