the third one and the last are probably best done as different modifiers the last is best done as a "rail" modifier ie 2 splines to describe the outline shape . the 4th is just a delete mesh mod on top of the mod ( or 3 seperate meshes 😕 )
the trick with these kinds modifiers in the sdk is to use the polyline (the visual representation extracted from the bezier) as the basis and not the actual bezier. Unfortunately to my knowledge this is not available in mxs (though you can approximate it). You then compute all the frenets (search the sdk and theres multiple versions) (array of xforms) a basis xform (computes the tolocal xform) as you can have more than one spline. There some really tricky maths for keeping a constant cross section (not included in the sdk versions 😐 ) and some post processing funkiness to make sure everything connects nicely in the case of a closed spline.