Hi Andrew
interesting Idea with some caveats as piercet and Andre already mentioned.
Thermal capacity and conductivity come into play here and as said before for 3D printing you want low thermal capacity and conductivity.
Those steel or copper filaments that can be polished… Do al of them actually contain metal particles? If so that might help to give you just enough heat transfer for your “branding”. Be careful: You have to stay with the Water bath temperature low enough that your model does not deform.
All the Best
Frank