The NZ Forces that went to Gallipoli were gathered from the existing Regional Forces in NZ; as you describe here.
I wrote a space page some time ago, to collect all those pre-WWl regiments & describe their history & name changes post 1914, but cannot locate it at the moment. It looks to me as if all the regimental categories are post 1914.
It would be good to have a collection of pre-WWl NZ Armed Forces categories.
The Anzac Sticker plus a link to individual Army Records is all I do at the moment for Gallipoli, found the lack of a specific Gallipoli cat. too bothersome to deal with.
I think a NZ Gallipoli Space Page would be the best place start, this would enable to get all info gathered in one place & organized before working on a category system. This, knowing that Regional Regimental IDs were amalgamated early in 1914 as the NZ Expeditionary Force was organized.
On a similar theme - A good place to start might be a parallel category for the Expeditionary Force that went to Samoa in 1914
https://en.wikipedia.org/wiki/Samoa_Expeditionary_Force