I change the plugin to show menus in "Plugins" Menu. Now we can set keyboard keys, is very useful to me.
I thought about a function of "smart drop" for all of the possible directions of the axis, like this, the aligned objects if they would not fix in the most distant part of the object of alignment reference, but they would collide in the surface. Look image example. It would be as the plugin drop, but it would work in all possible directions by axes(9 possibilities, or 6, if we not consider middle). Maybe some keys like SHIFT can change this behavior.