Before games are scheduled for slots, why don't you publish game descriptions for GMs and ask for preferences so that GMs don't wind up having no chance to get into new games that happen opposite games they run.
Although this would make it easier for GMs to get into the games they want, this would also make balancing out the slots a complete nightmare.
Example: If a particularly popular GM/game is running in slot four, then most GMs will want to avoid running in slot four, so they can play in the game or so that they can get good players. This, in turn, leads to fewer games in slot four...so everyone pretty much signs up for one game. This helps no one.