If they game has the element of being like a dream, it should be customizable, like:
1. You should be able to make your own character at least, and maybe other characters and enemies, if wanted
2. You should be able to make dream worlds of different sizes, like one for a single mission or an entire open world of many missions and free roam (a really cool, but simple idea for a dream would be to change the general colours of things, like set the colour of the plants or sky, day or night and things like that to make it dreamlike)
3. To keep it fun, maybe be able to make your own missions, and post them online for others. No difficult programming, just be able to choose the type of mission, (like...get to, rescue, destroy, protect stuff like that) make a space to play the mission or just put it on a place you've already made, put some mission like things in it, to make it harder and stuff like that
4. A simple thing would be triggers, like do a certain event or get somewhere and something happens
Like I said, I apologize if i'm being rude