Branflakes replied that one ship can mount multiple copies of DHCs, and other ships can use said cannons, but also qualified that all are subject to change.
So yes if you cry hard enough maybe it might not make Holodeck. I don't think its necessary since most science ships can't mount DHCs, but having it around gives ships that do mount it have more options.
Interestingly, mounting it on a dreadnought means you get to heal better without needing to switch power that often! DNCs might fail less.