Invocações de Eldritch (PHB, p. 107):

...Additionally, when you gain a level in this class, you can choose one of the invocations you know and replace it with another invocation that you could learn at that level.

Livro dos Segredos Antigos (BoAS) (PHB, p. 110):

Prerequisite: Pact of the Tome

You can now inscribe magical rituals in your Book of Shadows. Choose two 1st-level spells that have the ritual tag from any class’s spell list (the two needn’t be from the same list). The spells appear in the book and don’t count against the number of spells you know. With your Book of Shadows in hand, you can cast the chosen spells as rituals. You can’t cast the spells except as rituals, unless you’ve learned them by some other means. You can also cast a warlock spell you know as a ritual if it has the ritual tag.

On your adventures, you can add other ritual spells to your Book of Shadows. When you find such a spell, you can add it to the book if the spell’s level is equal to or less than half your warlock level (rounded up) and if you can spare the time to transcribe the spell. For each level of the spell, the transcription process takes 2 hours and costs 50 gp for the rare inks needed to inscribe it.

Supondo que o Mestre decida que os Rituais aprendidos pelo BoAS não desaparecem ao dispensar o (antigo) BoAS:

É possível pelo RAW ganhar dois novos feitiços rituais com todos os níveis de warlock trocando a invocação do BoAS pela invocação do BoAS ao subir de nível?

Bônus:

Supondo que o Mestre decida que os feitiços aprendidos com o BoAS desaparecem:

Um bruxo pode copiar um feitiço de seu Livro das Sombras para o Livro das Sombras e preservar os feitiços dessa maneira para obter mais feitiços rituais trocando BoAS por BoAS no aumento de nível?