The creative process of a project subsists of three parts. One, inspiration. Two, talking. Three, making the project. However, game developers tend to get all caught up in step two. They keep thinking and talking and revising, to the point where the project seriously deviates from what they imagined during step one. Talking gets even more convoluted if it’s a collaborative project or a big company is calling the shots. Anyone who has gazed wistfully at the concept art of game they were really excited about but failed to meet their expectation or was disappointed by the result of a Kickstarter they put money into knows this struggle.
Instead, it is better to go through the creative process steps one, three, two. Maybe the mechanic or artistry you envisioned in step one is unattainable, but it’s better to find out by trying for it and then working with what you were able to attain rather than talking yourself out of it before you start. It’s easier to work with something that already started than it roll with a blank page, anyhow.