"Use External Entry" option in the Itemstack Selector block

While working on NCX Tactical Additions, i noticed that the block had no option to use an external entry.

The option to use mod_id:item_id inside of the Itemstack selector instead of being forced to use a tag for every item i want cross-mod compatibility for would be greatly appreciated, as scrolling through hundreds of tags that optimally could be replaced by a simple reference is very inconvenient.