As a Roblox developer, it is currently hard to create some basic shapes without using CSG, especially cones, and also toruses and pyramids.
Even with CSG, shapes may not look as smooth as wanted, and if you want to change the model, such as make the radius of the shape wider, or don’t want it to be symmetrical, you have to separate the entire model, and meticulously angle negative parts around it to have the desired shape. This is time consuming in and of itself, but you also have the added likelihood of a union error, or going over the triangle limit. Example: Attempted “Cone”, really an octagonal pyramid, is irregular and looks terrible 
You could use a Mesh, but these are not compatible with normal part negation and unions, if you want to easily subtract or add to the shape within Studio, and are harder to scale. 
I propose that a few shapes are added to SpecialMesh, under the property MeshType. Adding Cone, Torus, and Pyramid could make building much easier and more efficient, like the current SpecialMesh shapes such as Sphere, Head, and Torso, which are extremely useful.
Current SpecialMeshes: 
Proposed shapes:
Cone (Mesh used to demonstrate scalability and symmetry) - 
Torus (Having the different sized inner radius of the hole in the torus, shown in the 3rd and 4th models, would require an extra Property along with the SpecialMesh) - 
Pyramid (Similar to the inner radius of the torus hole, Pyramids could have a Property for their base shape (triangle, square, pentagon, hexagon, etc.) - 
If Roblox is able to address this issue, it could make the game experience better by having shapes load in faster, as I am under the impression that meshes are more efficient than unions, and it would improve development experience by having a wider range of basic shapes that are scalable in the same way a normal part is, and that is compatible with unions, making building easier and more efficient.