[haste]

Sorry, but .buffFilter and .debuffFilter are for the filter argument of UnitAura. I could make it check for CustomBuffFilter and CustomDebuffFilter as well however.

The only changes made to the aura element in 1.6 is when :SetPosition() is run. Unless I've done something more and forgotten about it. :P

Using a backdrop would probably just be beneficial to layouts where auras only grow in one direction. There's also the issue with how it should handle multiple debuff types. It's also fairly easy for layouts to implement this.

The first thing you would have to do is replace :SetPosition() with a function that doesn't use the size of the main container frame to calculate rows and columns. The second thing is to update the size of the container frame based upon the number of icons shown. You can use .visibleBuffs, .visibleDebuffs or .visibleAuras to figure out that.