I have had no contact with Brainstorm. However, I do see them as a future secondary headliner at some point easily. They are headlining their own tour in Europe (Pagan's Mind in support). They were suppose to co-headline a tour with Evergrey (until they pulled out) so that puts them on an equal status as a previous headliner at this festival in the eyes of promoters. They sell more records than some of my controversial headline choices such as Jorn and After Forever. Plus, they assured their status with their last appearance here as they easily stole the entire friggin' show. They would jump to the top just as Edguy did at PP III.
Would the festival sell-out based on the Brainstorm name alone? Of course not. However, if there ever was a new headliner finally on the horizon in our genres, Brainstorm is it.