I think you are overestimating the importance of this table. It was merely introduced to have a rough categorisation merely for the purpose to be able to render an appropriate icon for it. Bindings have always been free to NOT define any category for a channel and have whatever item type defined for it as it wants - so this table does not put any constraints on the bindings, but rather wants to help them to have a well-suited icon referenced.
If the user can have either a ContactItem, or a SwitchItem, then how does the system reconcile this?
It is not the user, it is your channel type, where it is defined, which item type is the right one. So YOU can decide this, not the user.
If you want to allow the user to have multiple choices for item types, the way to go is to simply offer alternative channels to him.