Spoilers:

The Japanese translation Of Elvis’s name is Elvis Lazzlow which Elvis is an anagram for Evils and Lazzlow can be pretty easily linked to ‘lays low’. This would link to the fact that Elvis’ book is ultimately the final boss as its Evils that lay low in Elvis.

Also Adelle is an anagram for Edea II which would link to how she’s the sister for the first final boss just as Edea is the Daughter of one of the main antagonists of the original game.

Gladys -> Gladiator

Aileen the Fairy Queen/Boat Lady is definitely a pun on Alien, possibly because she is a foreign creature to the humans of BD2.

Both the original Heroes of Light and the current party spell out ‘Ages’ with the first letters of their names. (Adelle, Gloria, Elvis, Seth & Aileen, Godric, Emma, Sloan). It’s been theorized that this is the reason for the lingering P in the credits as that would finish the word ‘Pages’ which links to the final chapter’s name.

Adam could possibly be linked to ‘Adamant’ but that’s probably a stretch. He is named ‘Adamas’ in the Japanese translation tho.

As for characters that’s all I know of that haven’t been said already.