Let me get this straight or not - You are saying Subiaco WAFL Club to move up north to lets say Yanchep area to provide a future base for a third AFL Club.
Perhaps West Perth WAFL Club based in Joondalup with good facilities may want a say in that in the future. They are currently holding the fort so as to speak up there for our game.
The game has to expand and grow into new areas -That is a must. WA/Perth is likely to be hit with heaps of new migrants- Hopefully Skilled up- according to our very autocratic State Govt to fill the vacancies. But where are they going to live - Likely up to the Northern suburbs provided they bring some funds with them.
WA is a big place & the WAFC effectively control where the clubs play.
The OP needs to investigate where footy is played, not just the WAFL clubs.
WA footy funnels players through junior footy across the State & this feeds into WAFL Colts that is the primary feed into the AFL draft.
A 3rd AFL club in is no reason to change WAFL zoning.