With the advent of a new publicly-released TF2 sdk I think the question that's weighing on everyone's minds quite heavily is this: how do we make 6s more realistic? Realism is always sought after in the gaming industry and newer releases are constantly raising the bar. While I think adding lunch breaks for the mercs or even perhaps have them go on a period-accurate strikes and get killed by Pinkertons are both much needed injections, I can't help but think that the most appropriate change for such a movement and physics-based game is to update the format to match our current understanding of physics.
I won't pretend to be more than a layman on the subject, but from my understanding Einsteins Theory of General Relativity states that rather than space and time being separate but connected concepts, they are both a piece of one whole: spacetime. To add to this, the curvature of this spacetime explains our understanding of gravity and energy, at least in the large scale.
There are so many different gameplay implications to the theory of general relativity being applied to competitive Team Fortress 2 6v6, such as black holes or different masses for different unlocks changing how projectiles interact with you. However, given that tf2 already has a hard limit to the velocity that you can travel of 3500 hammer units per second (hu/s), or "maxvel", the obvious parallel is to that of the speed of light. Much like TF2, the universe itself has a hard limit on how fast one can travel: the speed of light, or c. General relativity states that since space and time are actually just spacetime, approaching the speed of light and traveling at such a fast velocity through space will then be accounted for through time, and time will in fact slow down so that that universal constant of c will not be exceeded.
I'm getting excited just thinking about 6s with spacetime, becoming the first multiplayer game with such a high level of realism, all in the best physics engine of all time: Source 1. In 6s, maxvel is not too difficult to reach, especially with an uber, so slowing down time for yourself will be both an extremely powerful and relatively accessible tool. Finally, both the sticky jumper and rocket jumper will become fully viable unlocks, and the already-potent strategy of a maxvel demo bomb through choke will become much more potent since the bomb will be effectively instantaneous from the perspective of the defenders.
Of course, there are some issues, just as there are issues with the theory of general relativity. On a small scale, these physics seem to work entirely differently, and modern physics is still searching to a unifying theory to connect general relativity with quantum physics, and that's a question that the tf2 community will have to solve. For example, rockets have no mass and no volume, occupying a single point. Do rockets behave like waves or mass-less particles? I don't have answers for these questions but i do think that if we as a community want to take serious steps towards bettering the scene, then implementing more realistic physics to 6s is the only obvious way forward.