1. Ability to set a base size for semisolid platforms:
With this, you can set the base width and height to any multiple of 32px (Default size is 96px*96px), this can come in handy for more complex semisolids
(Super Mario Maker/2 uses semisolids with a base size of 4x3 blocks, while the only usable base size in SMBX is 3x3 blocks). The following graphic shows, how this works in SMM/2:
2. Ability to animate semisolids:
For some reason, when a semisolid graphic is bigger than 96px*96px (but still 96px* multiple of 96px) and you want to animate said graphic, it's graphics glitch out.
The ability to animate semisolids would open up several new possibilities, such as resizable water spouts, Yoshi's Island cave platforms, etc.
3. Reimplementing BGO Blend Modes:
This would not only be useful to create sunlight or cave crystal-like effects, but is also not as CPU-heavy as using NPCs for such effects (using NPCs for this is also buggy, because they sometimes don't correctly overlap other NPCs (the graphics of overlapped NPC do vanish very often, if not correctly overlapped):