I come from Photoshop (on a PC), where the rulers have additional options (probably more than I know). This request focuses on three options that I regularly use. If the team decides they want to only implement one of them, then I prefer the Flip option.
1 - Flip guidelines with ALT key
When I need a guideline, I often select it from whichever ruler is closest to my pointer. In Photoshop I am used to holding down the ALT key, to flip that guideline to its alternate axis.
For instance… a guideline dragged from the top ruler can be flipped from its horizontal orientation, into a vertical orientation. And vice-versa for the left ruler.
Limitation to consider: ALT is currently connected to an option that shows the total pixels that one object is from another object.
2 - Snap to grid with SHIFT key
In Photoshop, you can select a guideline and when you press the SHIFT key, you can snap that guideline to the active grid.
For instance… when a 10px grid is active, you can drop the guideline exactly in 10px intervals. This SHIFT also works in combination with the previous ALT, so you can do both at the same time.
3 - Recenter Zero marker
Again from my trusted Photoshop, its possible to recenter your zero from both rulers, by selecting the top left corner of both rulers, holding down the mouse button and dragging the zero marker to reposition your rulers.