"meaning Jon went on tour knowing full well from the start that Richie wouldn't be able to make every show." is not the same as having a back up plan. I see what you're saying and it's kind of framing it like Jon shouldn't have done the tour if Richie had any chance of relapsing. Everything I've seen of Richie seems like it's putting on a brave face and going forward with the show no matter what. Listen to the rehearsals for the HAND tour when he broke his arm, you really hear him assuring everyone it'll be fine and he'll make it work.