GaaS is a flawed concept that cannot work as is.
A consumer wants a normal sized game that has periodic updates that provide more content. That would be sick. To the company, their is minimal value to this.
A business wants to make the same sized game but spread over a long period. Which means you get episode 1 of 10(maybe). Which to the consumer is pointless. Just finish the rest of the game and release it later. Additionally gaming companies don't have the tools to churn out content fast enough for GaaS either.
GaaS is a contradiction of a concept as is.
The solution is a hard one. Build tools that can allow a studio to build content faster. The day a company can build and release levels at the same rate as a popular sitcom or South Park, is the day GaaS could work.