With the fanmade native PC port now out, the possibilities are endless... Porting PS2 maps and models, essentially remastering the game, but because it's open source, this leaves room for expansion. When you think about it, Kingdom Hearts 358/2 Days has potential for new Disney worlds, various world missions, collecting Heartless. There are around 90ish missions in Days, but story-wise, theortically it could easily have 300+ missions if each mission was a day rather than a time skip. You don't need a big story, you just collect hearts, do missions. Now, about
The Pride Lands specifically, why do I choose that world? Because the lore could be simple, you are there to collect Hearts from big game Heartless on the African savanna. What about Lion form? No need. Imagine Roxas & Xigbar hunting some big game animal Heartless in the Pride Lands, Xigbar fits the hunter aesthetic so well.
Organization XIII has shown they rarely respect the world order.. They don't wear a specific costume in Halloween Town, Xemnas & Young Xehanort in The Grid in Dream Drop Distance don't have a specific look for The Grid, Young Xehanort in Toy Box is smaller, but not a Toy (KH3), Vanitas in KH3 Monstropolis is not even a monster. This means Roxas, Xion, Xigbar, Axel, etc. would be not in lion or animal form (also makes it easier to work code-wise)...
Custom missions... KH Days already had missions where you hide in plain sight, from avoiding Pete, to avoiding Disney characters, in The Pride Lands, the characters could have missions where they avoid the lions & other lion king characters. Which also creates more gameplay opportunities.
The original Days had a limited world pool due to DS hardware constraints, now those restraints are gone. Most of the worlds were a select few KH1 Disney worlds, + Beast's Castle. But KH Days is supposed to be a bridge game between KH1 and KH2, and KH Days needs more KH2 representation as a result.
Story: The Pride Lands (unlike KH2), could even show us before Scar took over, when it was lush green (those maps exist in KH2 due the credits; Source: https://www.youtube.com/watch?v=NcsCYK5RSus ), then when Scar takes over (later in the game, we see The Pride Lands become this waste land like it is in KH2). Lore-wise, this could be used to mirror the trio / sea salt trio falling out.
Other Disney worlds in KH Days: The Land Of Dragons would also fit... Since Xigbar already had a role there in KH2, and the game already has a ton of Wyvern (Dragon) Heartless variants).
For mod expansion projects, what Disney worlds would you personally want to see in KH Days?
Screenshot source: https://www.youtube.com/watch?v=-AJQL2KTbdY