I've missed the last few issues of the book--still on my phone, waiting to be read, so I don't know how much, if any, of this has been dealt with in the books-- but I'm almost certain that at some point SBP will make a fourth-wall-breaking comment about the legalities surrounding Captain Marvel's name, and how he's forced to call himself something else. From little images and scans I've seen it appears as if Billy is at least aware that some version of him was called 'Captain Marvel', and I think SBP mentioning that is one of the things will finally push Billy into taking back that name. SBP is DEFINITELY going to refer to Billy by his true name when they meet.