Something along those lines is pretty much your only option unless you want a rapier to be a player-only weapon and to use mission template triggers to capture key uses and play animations-on-demand for the rapier, overriding the animations that should be used. Weapon specific animations aren't possible with the engine, so you'll either need a hacky workaround like above or to abandon the notion.
Please use the stickied Q&A thread for questions of this nature in the future.