Some things I'd love to see in Super Mario Maker 2 *list incoming lol* (some of them was already discussed here):
-A better way to sort and score levels: Many people just give stars to musical levels, automatic levels and even troll levels so in the top list you hardly find actual good levels you can play. Nintendo did a good thing later on in the Bookmarks website introducing labels (classic, automatic, puzzle,...) but they have to put it in the game and make top lists for every category so you can discover levels you actually are interested in.
-When finishing a level the screen would let you give it a rating star/1to5 stars and a table of labels buttons to classify it. If most users classify a level differently from the creator, the players label should prevail for the curated listing in the game and 10/100 Mario challenges.
-In the same vein, when doing the 10 / 100 Mario challenge, you could be able to exclude some labels/types of levels so you can play difficult levels that are fairly difficult not because they're troll or kaizo levels, but good designed difficult ones. And if you're in easy mode you won't get only automatic levels or musical ones. This is necessary IMO if they're hiding some rewards behind completing the difficult challenges and people that want to start in Easy mode won't get bored quickly.
-Patches. Like someone else said, the need to upload a whole new level just to modify an old one it's awful (when they introduced checkpoints for example or if you wanted to adjust difficulty via player's feedback or the death trail, and losing all the stars you earned). The system could notify users that played your level that there's a new version.
-USB/Bluetooth mouse compatible. A pretty good alternative to touch controls (if they're are back), is the option to plug your PC mouse in docked mode. Including a capacitive stylus in a limited edition (or even a mario maker themed mouse) is other good option.
-Import your old levels via NNID/NO account. I'm not sure they're going to make all MM1 levels available when the game is out so I'd love to get a tool to import and adapt my old levels from the first game into the new editor so I can improve them and upload them as new if I want to or just keep them as reference.
-Include the Nintendo made levels from MM1, MM3DS and all the event courses (babymetal, CX, Zelda...).
-And a new campaign from Nintendo using all the new tools.
-A new improved tutorial with new advices for good design as we're unlocking new tools. The one in Wii U was good but too short.
-The option to include more than one sub-level and change if they're vertical or horizontal. A cool option would be you can choose the size of the level as 2x30 (2 screens high and 30 screens wide) or vertical (30x1) or even a square level (15x15) so you can make a single level with different orientations without the need of sub-levels.
-A layout view with all the sub levels and diagram of doors and pipe connections (a good way to keep control of a maze level).
-Increase the max length of the level.
-Optional infinite time.
-Pipes that warp in the same sub-level (not the transparent one that behaves differently and you can see the path they have).
-One way pipes, too.
-The option to change between different music (overground, antlethic, NES/SNES versions of themes...)
-Super Mario 1 and 3 All Stars skins.
-More color variations from levels (Underground, Chocolate Land SMW, several Ghost House themes, Castles and Fortresses, Ghost ship, Star World themes and skins for enemies... the amazing impressionist theme from NSMBU... the pyramid level from SMB3, giant world and pipe world or the grass theme from SMB3 1-2). Night themes.
-Fences with rotating doors from SMW castles and fortresses. Smashing columns. All enemies and obstacles from SMB3 and World..., ghost lakitu, eerie, statues with rays, mechakoopas, rotodiscs, thwimp... Oh, and the 4 way cannons from SMB3 Airships...
-More power-ups like Frog suit, Hammer Bros Suit.
-One or two more options for slopes (So you can make some hill shaped platforms like the ones in SMB3 1-2).
-Those semi-solid diagonal platforms from SMW.
-Include a check to make a level a boss one (so it don't have a flag pole or the bridge from castles and you can choose other way to end it). Or boss rooms.
-Include Koopalings.
-The option to design a map in the style of SMB3, World or else would be nice so you can upload a mini-campaign of levels. You could include the Toad mini-games to gain power-ups. And secret exits in levels to discover a second path on the map.
-More doors and pipes per level, please!
-And several checkpoints per level.
-Conditions to finish a level: hidden red coins or Yoshi coins, boss for example.
Andre's hard at work on it and it's looking to be a massive undertaking, shouldn't be long! Derrick's also very busy with a Fire Emblem analysis
We are waiting impatiently... :P