Circle commands

I've always wanted an easy way to make a sphere/circle/cylinder in minecraft. (not a perfect one but one you could get with world edit) Maybe a new command like the fill command such as /curve . some syntaxes might be:

/circle (type of curve) (center coords) (radius) (block it's made of) (e.g. hollow outline replace)        /circle       sphere              ~ ~ ~               3           minecraft:dirt                   hollow

/circle (type of curve) (center coords) (radius) (height) (block it's made of) (e.g. hollow outline replace)      /circle        cylinder            ~ ~ ~               3          6           minecraft:dirt              hollow

/circle (type of curve) (center coords) (1st point) (2nd point) (block it's made of)                                      /circle          arc              ~ ~ ~             10 4 10          ~ ~ ~            minecraft:dirt 

/circle (type of curve) (center coords) (radius) (block it's made of) (e.g. hollow outline replace)         /circle        circle                ~ ~ ~              3             minecraft:dirt             outline

Also, you could use this for the worldborder as well. For example:

/worldborder set circle (center coords) (radius)                                                                                     /worldborder set circle           ~ ~ ~            3 

Sorry this is pretty long but im sure many people will appreciate it :)