So! During the GM turn, "change the battle in a big way" doesn't have much in the way of limits! The three provided examples in the text are just ways to get started. 

The "default" setting for enemies and their moves is that the GM activates them in response to failures/partial successes after a player's action roll. But, if the GM wants, those moves can also be activated during the GM turn to make the enemies more dangerous (potentially letting them activate their moves multiple times/deal damage multiple times).  You could activate as many enemy moves during the GM turn as you want, depending on how dangerous you want those enemies to feel. 

There's not a specific rule for the order or which enemies act during the GM turn. I personally tend to lean toward less dangerous enemies, but for more balanced challenge, having the "bigger" enemies (striker/solo) also act during the GM turn and leaving minions out of it could work well. 

If you find that a particular enemy gets taken out too quickly, you can also use the GM turn to introduce more enemies (or maybe even play around with the idea of a second or third "phase" of the fight with strikers/solos/bosses).

If I had had some more foresight, some "swarm" or "large group" rules for minions would have been cool (might make it into a re-edited version eventually though). 

Hope that answered your question, but I'm happy to continue the discussion!