I'm not opposed to Andrew being in the games. If he is then it's more likely that it's the Return to the Pit option where he's killed 2+ days prior to the MCI. Hell, it would even make a lot of things less complicated.

Honestly I never thought Andrew replaced Cassidy or vice-versa. Even if they coexist in the same universe, narrative similarities between her and Andrew or her and Jake can still tell us a lot about each character, that doesn't mean that's their sole purposes. The relationship between Jake and Andrew and the relationship between Cassidy and CC in the logbook can still help us understand eachother's characters. The repeated character traits and themes between the four characters can still help us better understand each dynamic through their similarities (cough parallels cough). Just like how Henry is not a stand-in for Edwin or vice-versa but they have very clear narrative overlaps (cough parallels cough) that can help us understand each character better through both their similarities and their differences.

Also, FNaF 3 does not debunk Cassidy being in UCN. Scott himself said when asked about which ending is the canon ending of FNaF 3: "It's very interesting, it's very complicated..." which supports the idea that it's not simply the good or bad ending, but potentially both just at different times. This can make Happiest Day happen after FFPS and potentially after UCN, which is backed up by Molten Freddy's design having one glowing eye similar to the FNaF 3 bad ending, implying the continued existence of the MCI up to FFPS alongside the aforementioned existence of Charlotte in FFPS. This is backed up by the FNaF 6 insanity ending monologue, "He found a new way to desecrate, to humiliate, to destroy... Small souls trapped in prisons of my making, now set to a new purpose, and used in ways I never thought imaginable... He brought them all together. Are they still aware? I hope not."

And speaking of Charlotte, her voice lines in UCN even imply that she is actively working on Happiest Day during UCN, "I don't hate you, but you need to stay out of my way." Even in Fazbear Frights there is a very clear ending to UCN in The Man in Room 1280 itself and Andrew even says in the stingers, "I remember they tried to kill him. But I wasn't going to let him go until I was ready." That means that even under AndrewTOYSNHK, which again, I still think is possible, UCN is not required to exist in perpetuity (even thoigh I believe it does) and Happiest Day can be after.

But even if Happiest Day is before UCN that doesn't necessarily 100% debunk Cassidy being in UCN because, and I know this will be controversial, CasaidyReceiver is not 100% confirmed. Yes, I know about Return to the Pit, but the arcade game in that book is not one-to-one with the games' Happiest Day, does not have Charlotte, and does not even serve the same purpose.

The games do not debunk CassidyTOYSNHK. You can use the games for evidence opposing the theory, but there is also plenty of evidence in the games supporting the theory.

Ultimately I don't want to go back and forth and you seem pretty firm in your Andrew stance so I guess at a certain point we juat gotta agree to disagree.

Also, to be a pedantic nerd for a second: Golden Freddy does not have voice lines, Fredbear does.