After doing research and asking people, I don’t think any of these three things are currently possible. I think the first two would be easy to implement and the third doesn’t seem too terrible complicated, but I’ve never worked with Python or Blender code so I don’t know for sure.
1. Knife tool snap-to-grid/polygonal knife tool: I’d to be able to snap the knife tool to the grid for making accurate cuts and draw straight lines with the knife tool (like the midpoint knife but with exact cuts). Trying to make them freehand is so inaccurate it seems largely pointless to me, but if it were possible to align the knife to the grid one could make perfectly straight cuts along a given line or plane.
2. Snap object to gridlines by outermost vertex: If you’ve ever had a circle or cylinder off the grid and tried to align it to the grid, you’ll understand where I’m coming from. Holding control to snap to grid doesn’t actually snap to the grid, it moves in increments of the current gridsize - which means for an object like a cylinder where you can’t use “Snap selection to grid”, you can never get it back onto the grid. What I’d like is a snap-to-grid option where the outermost vertice is used to calculate the movment to the actual gridline. For example, if the user is dragging the selection to the right, the rightmost vertex (or vertices ) snaps to the gridline, and the rest of the vertices move the same distance.
3. Scale to gridline: This option would automatically scale the selection so that the outermost vertices are directly on the gridlines. If the selection is not perfectly square or round, the selection’s wider dimension would be used.