> Be as creative as possible [..]
This is obviously a trap. "Creative" comes from "creare" meaning "form out of nothing".
I conclude:<li>Programming languages where you only append and never delete make the most sense. Maybe something like a COMEFROM statement: "Replace line x with the following:"</li><li>The creation process should be automated, so one can create more. So... L-Systems for levels, items and stuff? Random generator? "AI"? Nah. Let the player (also) create things. Maybe scriptable objects to solve challenges in the game. But those objects then become part of the game.</li>