Mp3 support IS available in 2.25. It might be restricted in what format it is, but the first mp3 I tried worked just fine. Try with a different sample rate, and make sure it’s mono or the 3d wont work right.
But I duplicated “running” motions with NLA editor and editted them to “running + shot” motions to make in my WIP. this way has some probrem, but works fine.