In its day HMS Ark Royal carried 22 aircraft and a crew of 1,051 so it has plenty of space, especially with a few of these privacy pop bed tents on the air deck and a few of these Sleeping pots in the old crew quarters. With a popper fit out, I think you could comfortably hold 3,000 free loaders if not more.
Just anchor it off Christmas Island and let it also be a visual warning to those who choose to illegally come to Australia via a boat from Indonesia what their fate will be.
But sadly, this golden opportunity has slipped by. But for $550,000 US, why not buy these old “Whiskey Class” Submarines. Problem out of sight out of mind.