It's simple. As far as that list, Edenbridge, Helstar and Battlelore are NOT headliner caliber, period. It's common sense. Helstar has been around since 1982, and if 26 years later they're not ProgPower headliner caliber, I doubt they'll ever be. Battlelore would be a cool opener, and Edenbridge a nice band to see live too. Headliners? I highly doubt they'll ever reach that spot.
I keep seeing these bands mentioned over and over and I don't think it's from the same 3 people. Maybe not Turisas, but I feel like each of those other bands has been mentioned as a suggested headliner many times in the past. Either way, people obviously like these bands.
From the looks of the posts on this thread, PP can make a shift to putting more "mainstream-esque" bands on the roster in the headliner position - ala Opeth or COB - or Glenn can shift somewhat in the opposite direction and go for bands with larger catalogs, well received albums with good quality songs and those who have not touched the states or who have been here a limited number of times.
Regardless of what we all suggest here, Glenn continue to do what he has done in the past, drawing from all areas of Prog and Power metal (no matter how seemingly remote sometimes) with bands that could be argued for to fall into a number of spots on the roster, depending on what you are a fan of. Bands with 5 albums have opened (Manticora), bands with 5 albums have headlined (Sonata Arctica), bands with 10+ albums have played lower level spots (Virgin Steele), and bands that have played mostly covers have headlined (Jorn and in a sense JOP). But somehow as soon as Glenn announces a band, most of those who previously claimed that band "was not headliner/mid-level/opener/whatever caliber" are singing their praises by showtime.
I mean with the kind of expectations that folks on this board seem to have for headliners, eventually the well is going to run dry according these standards. Either that or we're all just going to be watching Everygrey and Symphony X headline for the 15th time.
That may be fine for some, but I'm sure Glenn also strives to keep things fresh.
Maybe all the bands 7th Saviour listed aren't perfect headliner caliber (yet) by everyone's standards, but I love how folks on this forum always seem to want proof or a source, but when I pose a question about why certain bands aren't "good enough" I get a "just 'cause" type answer for every band except Helstar. Helstar, I admit, you have a valid point about, but I've also seen bands see horrible attendance for regular US shows or tours, but then receive a phenomenal welcome at PP (JOP). I would also like to mention that not being as familiar with Turisas (although I do like their music) I checked their website quickly to check a few facts and saw about 6 or 7 albums listed in their discography, but later realized that 3 or 4 of those are singles. With that in mind, I can certainly see why they wouldn't be a suitable headliner, but I could certainly see them going over well at PP in another roster spot.
No matter what any of us guesses on this thread, it's still that ... just a guess. That is unless any of you has somehow managed to achieve a mind-meld with Glenn.