Some friends and I came up with a game mode that works half-way decently with any number of people: the more players, the greater the challenge overall but not to each individual, and can be played just fine with four people which is nice when you… only have four people. This game mode works well on MIRA HQ. We tried it on The Skeld and while we got it to a workable point, there are too many ways that random tasks can make things either way too difficult or way too easy for any given crewmate – the main issue here is that the reactor sabotage countdown on The Skeld is a whole bunch shorter than it is on MIRA HQ. I'm not sure that there's a good way to do it on Polus at all since Polus doesn't have a reactor that can be sabotaged and the Seismic stabilizer has a similar mechanic but can't be guarded.
1 common and 1 long task
Player speed 1.5 – 2.0
Any number of total crew
How to play:
Upon spawning, the crewmates immediately begin doing their tasks. The imposter goes to the reactor and, upon arriving, triggers the reactor sabotage to begin the countdown. If the players are on voice chat, the imposter stating "Reactor's closed!" at this point can be fun. At this point, only one crewmate is allowed in the reactor at a time and the imposter should kill any others who try to enter. This it to ensure that crewmates cannot disable the reactor, but tasks in reactor can be completed. A key component of strategy here is the crewmates with the tasks that will take longest after the reactor should be the ones to go first, for example, if two crewmates must redirect power and one is to med bay and the other is to greenhouse, then the one who has to run all the way to greenhouse should obviously be allowed to go first.
While this game is largely a mad dash to complete tasks, there's also a fair bit of strategy involved in terms of which tasks to do first and the order in which crewmates enter the reactor when necessary.
The way that crewmates win is by completing tasks, and the imposter wins if the reactor detonates. My friends and I have found that this is a great way to train on task completion for crewmates, and in random lobbies, we've been completing tasks first very frequently since we've been doing this. This game mode also lends itself well to the players being on voice chat, and cheating isn't really possible since nothing is being concealed.