OCTOLING INVASION
A mode where you get a team of yourself and 3 other Inklings and compete against another team of 4 Inklings to fend off waves of Octolings. I could see it as a combination of Splat Zones and Dr. Mario's Versus mode (probably something else, that's just the best approximation I can come up with right now), with armies of Octolings thrown in.
WAIT WAIT PLEASE JUST HEAR ME OUT
Each team would be on their own map, though their progress would be visible to the other team (by progress, I mean that the Inkling display at the top would shrink and grow depending on how many Inklings had been splatted on each team, cumulatively, and would flash Danger! if one side's Zone had been taken by the Octolings). Each team would start in the center of the map (except on Saltspray, where you would start in the topmost area with the boxes) and be assailed by Octolings armed with various weapons from both spawn point locations. The map has a Zone that the Inklings have to keep covered in their color ink for 8 minutes (usually where you spawn, but Saltspray has it in the area just beyond the starting point like it is in Splat Zones; maps with two Zones get one Zone that encompasses both Zones, except Moray, which switches to a single Zone in the center, and Triggerfish, which uses a single Zone and the Tower Control version of the map with the platform bridging the paths); if the Zone becomes controlled by the Octolings, your team has 10 seconds to get it back or you lose. Your team doesn't have a spawn point, instead spawning inside the Zone with a personal 2-second Bubbler that cannot be passed to teammates; splatted teammates cannot respawn when the Octolings control the Zone, so if your entire team is splatted while the Octolings control the Zone, you lose automatically.
The Octolings would start off fairly lightly armed, but grow in strength and numbers until they swarm the map and have mostly the powerful weapons. The Octolings' weapons include:
1) Octoshot, which acts like a Splattershot and comes with Splat Bombs.
2) Aerospray MG, which fires rapidly and attacks very aggressively and tosses Seekers.
3) New Squiffer, which can snipe aggressively and plant Ink Mines.
4) Kelp Splat Charger, which can snipe from a distance and toss Sprinklers.
5) Dynamo Roller, which can fling large amounts of ink and roll over areas and toss Sprinklers.
6) Rapid Blaster Deco, which shoots rapid exploding blasts and tosses Suction Bombs.
7) Octobrush, which can be swung for decent power, speed and turf coverage, can hold on the ground to run quickly, and can plant Squid Beakons, which act as an additional spawn point for the next wave (the AI will only plant these in designated locations).
8) Hydra Splatling, which winds up before firing powerful rapid blasts, and tosses Splat Bombs.
9) Tri-Slosher, a bucket that shoots multiple splashes at once, and slows Inklings with Disruptors.
10) Maybe others, as more weapons get added in, but I don't have any others that come to mind at the moment.
Each wave's Octolings vary from normal Octolings with any of these weapons, to Armored Octolings who have higher HP and only use Dynamo Roller/Hydra Splatling/New Squiffer (denoted by wearing the Hero Mode Armor minus the headgear), to Ninja Octolings who move slowly and only use Aerospray MG/Octobrush but are invisible while swimming in their own ink (like using Ninja Squid, would probably denoted by wearing something with Ninja Squid as its ability, or purple hairtacles), to Glowing Octolings, who tend to use the Kelp Splat Charger and Hydra Splatling and remain away from the fight (denoted by, well, glowing), and Elite Octolings, who use the Octoshot, have higher HP and deal higher damage (2-shot splat, compared to the Octoshot's 3-shot splat) (denoted by black hair and seaweed, like in Hero Mode).
The Glowing Octolings have a couple that spawn in each wave. These generally hang back, and will disappear if you defeat the rest of their wave, but splatting them sends a pair of Elite Octolings to the enemy team's side (one at each spawn point). Additionally, destroying the Octoling team's Squid Beakons sends a few Elite Octolings to the enemy team's side. Finally, if one team manages to capture one of the enemy team's spawn points (you can do this by inking it until it changes to your control), the rest of that wave (that came from that spawn point, Octolings who came from a different area or a Beakon will remain) disappears in a puff of smoke and is dropped onto the other team's side (except Elite Octolings, those remain on your side once summoned until they are splatted). However, if a spawn point is captured, that point becomes Octoling-controlled again at the start of the next wave, with a spawn-point-shield around it for 1 minute, and the Octolings who come from that point have a 4-second Bubbler that cannot be passed to other Octolings.
If one team loses control of their Zone for 10 seconds or has their entire team splatted during the 8 minute time limit, that team loses by Knockout. To decide the wining team if both teams survive for 8 minutes, the team whose Inklings were splatted the fewest times wins. If both teams have an equal amount of splatted Inklings (or none) when time is up, then Overtime begins. During Overtime, both Octoling spawn points gain spawn point shields, and an overwhelming number of Elite Octolings pour out of the Octoling spawn points and any Octoling Squid Beakons until any Inkling is splatted (in which case, the team whose Inkling was splatted loses) or until one team loses control of their Zone (in which case the team who lost control loses).
The stages would just use the Splat Zones versions of the current stages' maps, though with one Splat Zone in stages that had two, as covered earlier.
, and 75% resistance to 
