Question about "air" tiles (invisible tiles)

[Hblade]

Is there a way I can make it where if I click (or right click) on a tile thats made up of a transparent frame (Example no pixels in the frame at all), I want to be able to have real air tiles. My workaround so far is to have an incredibly transparent tile (.1 transparency on gimp) making it almost invisible but this generates a massive performance drop

Anyway, say I have a big clickable box, right? (filled region) and I right click it, I want it to be able to copy the tile -behind- it if that makes sense?

EDIT: I might have found a way to do this but I'll love to hear your guys' ways =)