I havent had the opportunity to test neither of the new megas yet, but I feel like special Altaria could have some potential in the current meta, especially if paired with Dug. Its good typing and natural bulk lets it pivot into some threats like Zard Y, non Ice Beam Ash Gren, most Keldeos, fat Landos, etc to start punching holes on the opposing team. The combination of Hyper Voice and Fire Blast is actually not that easy to switch into and most of the mons that come to mind like Chansey Toxapex Magearna are trapped by Dugtrio. Celesteela can switch into it once but if theres something to stop leech in the back like Tangrowth, it wont be able to recover enough health to avoid the 2hko the next time. Tangrowth needs Sludge Bomb to threaten it, otherwise its just going to sit there and slowly faint. Access to Roost is nice because it can 1v1 these passive mons like Mew and Tang that can take hits but not do much back. On the last slot I could see something like Heal Bell working, or even Facade to switch into burns and put more pressure on Mantine. It could probably work well with something like Ash Gren or Scarf Lele that appreciate these special blanket checks weakened or gone while further abusing Dugs trapping capabilities and also pressuring some other bulky mons like Mantine that annoy Altaria. Its by no means gonna be a top tier Mega but its gonna have some use I think, though I dont think its DD sets are gonna be that good.