Requests:
1.
4-point fisheye perspective ruler.
At the moment you can create two fisheye perspective rulers, one vertical and one horizontal. However, it is difficult to line them up correctly and takes a lot of time to setup. See here for the current possible setup.
2.
Flatten 2-point perspective/more solid rotation and snapping options.
This could be done by selecting and transforming perspective points so you can rotate easily and snap to angles with shift modifier key. I am aware that the 2-point perspective allows you to snap to angles when you first draw it. But after you apply it there is no way to snap it back to 45-degree angles.
Video in Clip Studio demonstrating perspective tool rotation snapping and disabling individual perspective points.
3.
Option to snap to centre. Specifically useful for single-point perspective. But in general, Krita needs better centering options. See here: Centre raster layer on canvas
4.
Level up improvements:
Perspective ruler as a layer in the layer stack so organising can be done as well as the ability to create a group where only the ruler is active within the group. For example, this would allow you to draw a cityscape where some buildings have separate 2 vanishing points (very common in cities especially ones like Tokyo where nothing is a grid).