THIS IS SO FUN-Ok, so, for worlds, I'm thinking you could have Glory Hounds, Burrows, Temptation's Ballad, Adastra, The Hayseed Knight, Echo (time travel gimmick to allow all eras), Nekojishi, Clawstar, and The Pirate's Fate. I think that covers a wide range of genres! As for my party, I'm picking Dawn Hound and Eina! That's a team that's gonna kick some serious ass!
The partners you could choose from every world would be: Glory Hound's Dawn Hound, Burrows' Grey, Temptation's Ballad's Cole, Adastra's Amicus, The Hayseed Knight's Eina, Echoverse's William, Nekojishi's Likulau, Clawstar's Elijah, and The Pirate Fate's Mila.
Also, here's the summon I think you would get from each world: Glory Hounds would give Milo, Burrows would give Ken, Temptation's Ballad would give Hamish and Marrow Bonebreaker, Adastra would give Neferu, The Hayseed Knight would give Gyof, Echo would give the electric socket monster, Nekojishi would give Guardian Tiger, Clawstar would give Tremor, and The Pirate's Fate would give Darious.