Here are the main problems:
- The mechanic doesn't drive player attention;
- The mechanic doesn't help user retention, drive income, and make surprise;
- The programmer and artists cannot figure out what to do based on the design;
- Cannot work out the UI/UX based on the design;
So check points for different parties:
Producer and Operations:
- Is the mechanic worth to work out? (.. ROI)
- Can user retention be improved?
- Can it drive income and How much will be?
- Can the new mechanic cohere the main gameplay?
UI & UX:
- Can work out the game flow based on the design?
- How the new mechanics associate with other UIs?
- When will user learn it and How can to learn?
- Can the design tell the assets need to produced based?
- Can the assets production meet the deadline?
- Can work out data design based on the game mechanic?
- Can work out program flow based on the game mechanic?
- Is the mechanic contradict itself?
- Is the mechanic too complex so that it is gold plating (over-polish)?
- Can the implementation and testing meet the deadline?