I'd like to suggest a hook like ThinkFrame which would run on all frames of the game, or if that's not possible, maybe hooks for the different areas of the game, like for example the intermission screen, the fade cutscene, the main menu, stuff like that, so modders can have a little more freedom on what can be done.
Right now, no hooks except for maybe the chat hook and the player join will run when the game is showing the score tally, and even then there's no way to detect if players are playing or waiting for the intermission to end.
Maybe a timer that always increases, even while the game is lagging and everything's frozen, so timers can still run no matter if the game is experiencing problems. Sounds desynch prone, but with some magic it can be used for something neat.
Maybe also give the ability to modify the intermission screen, both in Co-op/Singleplayer and in match gametypes, just like we can modify the HUD while in-game?