Object, I don't think you can. maybe using some exploit to use an "object" costume on a NPC ? I've seen a bugged console in KDF academy, with HP bar and "Bekk" as name, so it is possible, not sure if it is using the foundry.
For the contact becoming an hostile, you can do that. Use the contact, and make it hidden with the appropriate trigger, then have hostiles with the same costume that "appear" with the same trigger, on the same place. It's not perfect, but it work.