RPGMemes

I have actually personally done a subclass multiclass for a player in a game I run, but it was a very ad-hoc "okay it makes sense for your character to do this, so you're just getting the level 3 feature from that subclass and the level 7 from this one, and this is how they interact" deal

I suppose I'm trying to think of how I would present it for games that I'm not involved in or don't know the other players in. Something worded cleanly enough to stand up (at least a little) to situations when you can't necessarily fall back on trust between the people at the table