Random thought, I've been adding billboards that require accurate placement, and over time I've had to adjust the sizing. I can imagine a feature where you can add alignment guide lines (think Photoshop) where you can set distant ratios between objects precisely.
The functionality that Photoshop provides would be the desired feature set. Add as many alignment guide lines as you'd like, and have the edges of sprites / billboards snap to the guides, with the ability to turn off snapping.
Just a thought as I'm re-positioning and re-sizing billboards frequently,