Additionally: Good luck getting some officers to prefer limping over to Medbay after dealing with a criminal when there's a questionably qualified doctor not three yards to their left. Telling an Brig Phys to specifically not heal anyone but prisoners is, as mentioned, a breach of that delightful Hippocratic Oath but as well crippling security in any situation where they will inevitably need surgery after dealing with the issue (Shadowlings, Terror Spiders, any high damage antagonist.) Brig Phys is also already restricted by what they can get from other departments, as I know all to well. If a Brig Phys doesn't need a cloning pod/cyro tube/chemistry station, then the respective department for the materials could easily tell them "No." And then report them for B&E when the doctor tries to get it themselves.