Scenario 1:
With James and Ozpin wanting to make him a Hunstman and, for whatever reason, not thinking he's already qualified for the position, the Doom Slayer is sent to Beacon academy, where this 30-to-40-year old looking man is sent to join Team RWDBY (Pronounced Rudby, with a silent D). He then joins on their adventures, shocking and horrifying people with how cool and violent he is, but everyone likes him anyway despite the fact that a number of these people would be morally against that level of violence when applied to people. Despite the fact that they've been joined by a highly skilled and incredibly violent individual, most of RWDBY's missions go exactly the same as in canon, except with a lower death count of named characters for some reason.
Never do this. Only Demons do this.