Okay, I found an old "dream doc" I made back during Mario 3D World's release about my ideas for a sequel...
Obviously it'd be called "Super Mario 3D World 2", with the 2 referencing Mario Bros. 2/USA.
It's mostly mechanically a straight-sequel to 3D World, with Mario, Luigi, Peach, and Toad returning as the playable characters functioning mostly the same, except now they can pluck items from the ground and lift certain enemies, carrying them around and using them as projectiles. Rosalina does not return, but clearing the game unlocks Imagin, Mama, Lina, and Papa from Doki Doki Panic, who fuction as palette swaps except they have two hearts instead of power-ups---thus the game is a bit harder as them. Technically Fuji TV I believe owns them, but maybe Nintendo could work something out?
The game's plot involves Subcon re-imagined as a storybook, which has been destroyed by the Musical Maestro of Mayhem, Wart. Poki and Piki, Imagin's youngest siblings, escape and enlist the help of Mario and co. to restore all the pages, and thus the adventure begins! Bowser follows as well, but is quickly overpowered by Wart and turned into a frog, which he stays as for the rest of the game making small cameo appearances, with his Goomba changed into "Goombog", Goomba-frog hybrids. Likewise other classic enemies would have a froggy makeover.
The World Map, which felt pretty weak in 3D World, is ditched in favor of a non-linear "solar system" of levels where you choose your own route, with Mini-Boss and Boss Levels blocking your progress. To win the game, you need to reach all the Boss Levels and clear them all to reach Wart, so there's a variety of paths you can take. Each level has three hidden orbs which are used to unlock new paths on the world map through Bird Gates, so you can determine how you want to play---stay on the linear route level-by-level, or jump around by focusing on collecting Orbs? You fly around the world map on a book page that acts like a magic carpet, and at the end of each level you jump on a missing page and fly off---no Goal Post Bonus this time around, but carrying an item or enemy to the end will result in it changing into a power-up or 1-Up. Some special enemies must be carried to the end to receive an Orb.
In addition to normal levels you have levels specially made for one of the four characters, testing their skills to the limit, as well as levels where you're locked into a suit testing your skills with its power. Challenge Rooms also return.
As it's a storybook, the levels this time around are themed on fantasy and such---you got Arabian-inspired settings, fitting the original Doki Doki Panic, you've got feudal Japan, you have castles, you have Christmas-themed levels, etc. A bit more "grounded" than Mario 3D World was in its design, though still "game-y" with lots of floating platforms and the like.
The Super Mushroom, Fire Flower, Double Cherry, Mega Mushroom, and Star Mushroom return as do four new power-ups...
* Frog Suit: A remodeled version of Mario 3's, now with a mouth under the nostrils that can lick up items and enemies and carry them---this allows the wearer to keep all their athleticism which is usually nerfed when they're carrying an item by hand. It can also jump higher and farther, and underwater gives the wearer far more control, speed, and the ability to carry an item while swimming, as normally a character would simply sink. They can also run at normal speed along the water's floor too!
There's an upgrade known as the Prince(ss) Frog Suit which adds a golden crown, and can do a ground pound that turns them into a golden frog statue---and for another Nintendo frog reference, the pose is that of Prince Sable's. Killing enemies with this turns them into 1-Ups, useful since it would appear in the difficult bonus levels.
* Ninja Suit: The Ninja Suit allows the wearer to move at faster speeds, running up walls for a time and crossing water! They can also perform a powerful angled kick to strike down foes. Useful when you need some speed, and fun to speedrun with.
* Knight Suit: They can deflect weaker enemies, though they're vulnerable to magic attacks. They can also create a shockwave through ground-pounding. Though slower and not skilled at platforming due to the added weight, when sprinting they put their shield forward allowing them to break through obstacles and pass through certain barriers, like spikes, unharmed.
* Clown Suit: The rarest, this allows the wearer to summon a large ball when they aren't carrying anything that can be ridden on over lava and poison, and speed up down slopes, plus bounce away weaker enemies. The wearer can also deploy a balloon when jumping to far off platforms allowing them to float, but it'll pop if it touches a foe.
Anyway, Wart returns as the main villain and is re-imagined as a pipe-organist, with a bit of Phantom of the Opera flair---his new motif incorporates the Frog Song of Soul tune from Link's Awakening. His army consists of Shy Guy, standard foes you can step on and then pick up and throw them like in SMB2, frog-mutated classic enemies, many obscure foes from SMB2 that haven't returned since, and the 8-Bits, with the four Birdo Sisters and four Mouser Brothers serving as the mini-bosses in place of Boom Boom and Pom Pom while the bigger bosses are brand-new enemies for the most part. Also Ninji is back as are Dino Rhino, which you ride on in certain levels.
