Conquest
Splatoon maps are generally small and contained because of the game’s focus on quick and short matches. However, there’s no reason Splatoon couldn’t be a prime candidate for larger, more expansive matches as well. Particularly, something similar to the Conquest mode from Battlefield. This mode would require new larger maps than the ones Splatoon 2 currently has, with different zones and sections. They don’t need to be as large as the maps we’d see in something like Battlefield, and the mode could still use 4v4 teams.
A Splatoon version of Conquest would see one Inkling team attacking an area with another defending. The attacking team could have to ink a set amount of turf in the allotted time, while the defending team’s only goal is to keep the turf their color. If the attacking team can take over a significant portion of the area, they’ll move on to the next area. Of course you could go more Battlefield style, and just make the attacking team hold one or more specific areas to move on. The key is that the focus is Inking territory through multiple steps and phases.
