I have some more ideas for you.
A noble Dragonness you can meet in the port town, if Scayla is fat enough she mistakes the player as a fellow noble. allowing the player to hang out with the noble court, but be careful because if you stay too long you may be too fat to leave. you can deflect the offered meals onto the other members of the court, fatting them up.
Add dialog for when taking a looong nap, describing Scayla curling up/laying down in different locations depending on the location it was initiated in. with different descriptions of Scayla depending on her weight.
Add the ability to successfully steal the red dragons' amulet or be given the amulet if they make Scayla their wife. but it is cursed to passively fatten up the wearer. either keep the amulet to yourself or pass the curse onto another.
Maybe add a pack of fat boars to the forrest that can be located by chance, if the player wins the fight they can eat the entire pack for +1000 fullness. but the fight is not an easy one, if the players health/armor isn't high enough they can die.
Add a temple in the port town to the dragon goddess, who is a giant glutton. if you die you meet her, with a high enough intelligence and chonk stat the player has the chance to impress her. doing so allows the player to respawn in the temple, not impressing her gets Scayla eaten and the usual game restart.
Add minibosses to different environments that the player can either fight or run from. beating them gives the player an item of great wealth that can be sold and the option to eat the defeated enemy.
Add a food stall to the port town or village, with the option to steal some pastries. if the player is skinny enough it is a successful heist, but if the player is too fat it ends in being arrested by the guards. if arrested Scayla wakes up in jail, and has to look around for items to help her escape. However she has to be quick, for the food the jail serves is designed to fatten dragons up quickly. If Scala gets too big she won't be able to escape, and the cell has a mirror placed in it to see just how big your getting.
A successful heist introduces Scayla to the thieves "guild", but they look more like a ragtag group of boored teenagers and actual thieves. They want you to help them make it big, with a heist of the local Nobles hoard.
Most of these things are do-able in terms of coding them in, though others are not, like the Respawn Temple thing, or some time-limited things, since the engine is mostly made for linear games and not something like this. I'll try to implement the stuff from your reply that I find cool/interesting, in one way or another.
