Just finished the prison.
Before Deling city there's already access to Death magic on world map. Perhaps overkill for disk 1?
Another unbalanced magic is Tornado, by converting Abyss Worm cads into windmills. Makes str go way high.
Armadodo and T-Rexaur also give access to Dino Bone which gives access to Quake.
Loved the new battle on winhill. You could add a few dozen more

it would give more new content. There are quite a few monsters you will only see once in the game (like some castle bosses). Perhaps add a low level version here and there

In the prision, the human guards do only one attack (stop). Is this intended? With 3 members its easy, but that screen with only zell it's a coin flip.