I don't know if this is possible to implement or already on the "to-do-list", but especially in larger levels it would help to be able to zoom in/out. The mousewheel would be the obvious "hotkey" for this.
Maybe sth like x0.5/x1(default)/x2 zoom factor would be good steps. :)
x2 is helpful in precise assignments where you need to see every little pixel.
x0.5 is nice to have to get an overview over large especially vertical levels.
Nice suggestion. To avoid duplicating effort, I think it's best to put this one on hold until I fix the windowing issue, though.