I'm solidly against any artificial limits on the GM in an effort to make it more of a game. The biggest draw of a GM mode should be the greatest amount of freedom possible. At most, they should make it possible for modders to add that, but they shouldn't spend any effort themselves on trying to balance a game mode like that.
Here are the templates/tools I'd like to see, from most basic to the more difficult
Start a timer or turn counter that displays on the screen for the players
Random number generator
GM text that displays in some special box or on the bottom of the screen somewhere, or GM can also talk through an NPC and bypass its stock conversation options. Players would probably have to type or speak their responses instead of selecting from a list, since that'd be impossible to whip up on the fly.
Add a journal entry to all or some players, using either preset journal entries or ones you write on the fly.
Private communication with certain players
Mark ownership on items and move them around
Add and manipulate triggers
The ability to change the atmosphere, at least to a preset value, but modifying all the values would be awesome.
Ability to see all active timers in the code and pause or start one (probably only timers that are marked as GM-changeable to prevent situations where a GM breaks a quest or system.) Situations where this would be useful is if you had a day night cycle, and you wanted to bypass that to skip ahead to morning from night to indicate the players had slept, for example.
Quest templates for basic kill and fetch quests, though I'm actually skeptical about the importance of the ability to make quests on the fly. After all, a quest in itself doesn't really mean anything, it's just used to symbolize that there's a task. But if you have a GM indicating there's a task, and reward you for completing it, you don't have as much need for the code (though obviously it's nice to automate things if you're trying to do a lot at once, and conversation coding is still important to make NPCs say different things if you've completed a task.)