I always wanted a simulation of the game to test out what certain things will happen in certain interactions. Most of the time, you don't have 6 friends with you to try something out in a custom game, and most certain unknown interactions happen in the Coven DLC, and chances are, you won't have 6 friends that have it, including you.
In this simulation, there would be one player controlling all 15-7 roles' votes and abilities. The day-night cycles will be shortened, there will be no Discussion and Defense. There would be no timer, and the player would manually start the next phase.
This simulation could also help new players figure out common interactions, and not call other people out from something totally normal. This could or could not be free. You aren't even playing the game, just seeing how it works.
This would help a lot for new players who barely know any interactions and have learn them second handed, which I always disliked when I was new, and would also help many curious players trying to find out what would really happen in obscure scenarios. This might also help the developers, because if they were to semi release new mechanics to the test place, people could find bugs 10x as fast, instead of having to play with friends to test out every single scenario, or play normally to lower your chance of encountering a bug tenfold.
For example, what would happen if a Transporter transported a Pestilence's target with the Pestilence. Will the Pestilence attack themselves, despite it not doing anything? How many times will the Transporter be attacked by the Pestilence? 1,2,3, or 4 times? (This is because Pestilence rampages at home and at the target) This is an example, you don't need to answer it.