This is already happening at scale by the social media feed algorithms. We don't need generated content to accomplish this. In a sea of user created content, plenty of it is already at peak activation.
There's algorithmic ways to accomplish the same thing without requiring monitoring of the brain, if there's enough data to pull from. Semantic analysis + engagement monitoring is more than enough. Peoples emotions expressed via comments is a reflection of brain region activation.
The end result of this will be that creating viral or maximally converting content will not be restricted to the top content creators. It will also result in down regulation of those brain regions due to constant stimulation, so the bar will increase for what classifies as attention grabbing and the brain will filter most of it out as noise.
All in all, I don't really see this being a big difference to the outcomes we're already seeing.