Having some form of asset copy protection would be nice but no technical solution will ever be perfect and ultimately this is a legal (intellectual property / copyright) matter … nothing beats clear “terms of use” and, if needs be, a choicely worded “cease and desist or takedown” letter.
Personally, I think just splitting up assets into more granular chunks (modular sub-meshes, textures, animations etc) then using the Assets Manager to load and assemble (mix and match) the assets in game would make stealing things more trouble than it’s worth for most people. I know it’s a bit more work but I prefer this approach, irrespective of the copying issue.