NOTE: This is something I know is not currently feasible, it's more of a far out goal that I may come back to at some point
Remove all existing content so we don't have to worry about supporting every user made thing. It is near impossible to keep track of all the ideas we have gotten in the past two decades, but it would be good to round up the good ones (places like the SuperTux media directory and grumbel’s filesystem have great ideas and concept art in them)
New engine that is easier to utilize and contribute to, the current one seems very difficult to get into or understand. This may clash with the more ambitious game idea, so it depends.
Opportunity to simplify and improve existing ideas when re-implementing them
Powerups could be adjusted, it would make much more sense if the mushroom equivalent was a fish instead of an egg
Make coins have a purpose of some sort, possibly add item shops in the worldmap where you can exchange coins for rare or even exclusive powerups
Re-introduce level timer for extra challenge or incentive
Rework the lives system, having coins as lives is too unclear and difficult to gauge
More interesting usage of lightmap for puzzles
Potentially integrate lost ideas like Granitos, Evil Penguin (Birdo), factory/industrial level theming, etc.
Better menu design than just a list of options, maybe get inspiration from things like Pingus?
Make character animation smoother and more expressive
Properly represent characters like Nolok and Penny
Larger, more interesting decals and set pieces with animation and effects like torch fire, waterfalls, etc.
More moves for Tux to pull off? This might not be needed and only complicate Tux’s moveset, it depends.
Water that Tux can swim through, perhaps like Penguin Mario where you control direction and flap your arms with action for a boost of speed
Vines that Tux can swing back and forth on, think NSMB.
Sliding like a penguin down sloped surfaces, much like how Sonic rolls across hills. Might stray too far from current gameplay, it depends on how much we want to change things from a tile-based Mario platformer to a more Sonic like game with more freeform geometry and advanced physics
Autoscrolling “avalanche” levels where a horde of enemies like rolling snowballs or boulders chase Tux, make scrolling faster depending on how far Tux is from the edge to keep a frantic pace
Shaders for fire, water, god rays in the forest, proper lighting engine that makes light stop at walls instead of acting independently of terrain
Lightmaps to provide more realistic visuals like SuperTuxKart?
Use of puppet tools, 3D models or some alternative to more easily and smoothly animate characters? Alternatively, we could keep the hand-drawn animation and lean more towards that style for the visuals.
Support for larger, more freeform tiles that look more dynamic, like large rock faces with varied patterns. (see images below)
Potentially remove tiles altogether and come up with a new method for drawing terrain, maybe something more freeform like Sonic Studio? Perhaps use a very fancy script to fill ground shapes with a set texture and place tile edges around them?
Improved level editor that can place ground on a grid in different shapes, like full tiles, slopes, possibly even freeform shapes?
Have water be more dynamic than simply a tile, have it splash and ripple at the surface, use some sort of fancy tech to render it as a volume instead of using single tiles
Ice floes that tilt depending on the player's weight, and bob up and down as the player lands on them
Fix slopes, make them easier to traverse and stop things like enemies failing to walk up them or treating them like walls