I love the Volcarona idea and the Scarf lele. Could make a psyspam team w/o Zam Tysmnon-HP Ground Volcarona (especially Z Psychic sets with Bug Buzz and Fire Blast) as it can lure and chip/kill Heatran and Tyranitar for that variant of Volcarona stands out to me. However, some other Pokemon include Scarf Tapu Lele, Toxapex (gets trapped by Magma Tran pretty often, but doesn’t always fit on M-Lati teams), and even other stray Psychic types like Hoopa or Reuniclus who want to abuse Tyranitar being lured.
Always forget to check that. Oopshttp://www.smogon.com/dex/sm/pokemon/latios/
See team options in the Mega Latios section. Magnezone helps remove Steel-types like Ferro & Celesteela that don’t really care about any of its moves, while other options like Kartana & Tapu Lele appreciate the Pokemon that Mega Latios weakens, for example.