You currently have no chance with a skilled independent visa as Aeroplane Pilot does not appear on the associated Skilled Occupation List. Instead you will need to find a state that has Aeroplane Pilot on its' state migration plan SOL and apply to them to be nominated for a Skilled - Nominated visa. Once you've got the nomination you can apply to be considered for the visa (EOI -Expression of Interest) through
SkillSelect, I suggest you have a look through that site and work out if you can achieve enough points to qualify before you start down the license conversion.
I can't tell you what qualifies as significant experience and, more importantly, neither will CASA until you hold an Australian license - catch-22!