The workflow I have in mind for is "incremental gameness"

1. have an idea for a simulation
2. implement it in the IDE using only the default interface
3. slap an easy, menu based interface on it to get some kind of player interaction going. iterate until fun
4. implement a minigame for a key aspect of the simulation. iterate until fun. repeat until you have a minigame that is more fun than the main game
5. redesign the interface around the minigame. while you're at it, make it pretty
6. in fact the default interface kit isn't doing this game justice anymore, let's rewrite the frontend in Unreal
7. video game