Might VR boxing be a possible alternative to actually being hit? I don't think our brains distinguish well between actually being hurt and feeling the stress of the game. For instance I used to study for tests while my husband played violent video games with loud sounds because all the screaming was stressful for me and so was actually taking the test. So the combination of studying under stress and taking the test under stress helped me retain the knowledge better.
I have no experience with VR boxing but I can tell you there's no comparison between e.g. a tournament Karate match and first person shooters. I never heard about this idea that studying under stress can help you perform in a test...