In the US Tool is definitely at about the same level as Maiden. They are radio staples and have several very well known songs. They play similar arenas on tour. I would even say they are possibly the most mainstream Metal band to come out of the mid 90s/00s. Again going back to Power Trip, the fact that they were the only non 70s/80s act on the bill says it all.Don't know if it's the same in the US, but at least around here there's definitely a lot of crossover of Maiden and GnR fans in the general populace, which is mostly old geezers (either actual ones or spiritual ones), which is the case with rock in general (although Metallica are really good at bringing a lot of casuals who know mostly Nothing Else Matters and Mama Said, primarily on name recognition alone).
So from a marketing point of view, that would seem quite logical and might have quite a pull, however I can't somehow imagine the bands cooperating much, they give off vastly different vibes and I wonder if having Bruce and Axl on the same stage is a good idea (didn't they have some feud too?)
Tool... unless they somehow have a much bigger crossover appeal over the pond, I can't imagine that. They're a much more niche band than even, say, Dream Theater and at least to me they feel like they attract a completely different audience. Despite being technically "prog", I see them vibing more with the Nine Inch Nails or someone from the Lollapalooza crowd, but maybe that's just me.
BTW how about DT themselves? They toured with IM in the past, DT members are fans of IM, 'Arry used to like DT himself, they're both moderately successful with the public and they feel compatible, melody-wise, spiritually... Also, with Portnoy kinda bridled nowadays, there are probably no competing personalities.
If there wasn't the history with Ozzy/Sharon/whomever (but then again, Axl and Bruce also had problems with each other - little wonder) and if they weren't simply too old for anything, Sabbath - Maiden would seem a really good match.
DT isn’t even really in the same league, they are a midsize theater act at best. Even on their current reunion tour they’re not filling up the arenas, last I checked the upper bowl of O2 wasn’t even on sale (and probably won’t go on sale). It’s also worth mentioning that when they opened for Maiden in NA in 2010, Maiden themselves hadn’t yet fully upgraded to arenas. They were still playing amphitheaters on a lot of those dates.
It’s possible. I’m skeptical that GNR can sustain the crowd sizes with the amount of touring they’ve done. They have already downgraded their venue sizes a bit on last year’s leg.Think GNR would be in the same bracket as Metallica and AC/DC, i.e. Maiden are never going to be headlining over them. GNR don't need a package for stadium gigs.