You have to be joking. The buses only run every 20-30 mins, so if you miss one because your bag took a while to appear, you've a wait on your hands and suddenly a very tight transfer. Also, they are picky about who can get on (you have to have a printed, paper intinerary, none of this new-fangled phone business is acceptable), so whilst the buses are reasonably comfy, it is absolutely not a service designed for constant use. It is designed for the very occasional transfer punter; there is no way it could cope with the numbers. A same-terminal transfer is a no-brainer. In any case governments use taxpayer funds to invest in lots of things on a regular basis, this is no different.
Possibly. Surely it would be MUCH CHEAPER to upgrade the bus service, especially as we are talking what, TWO flights a day, than upgrade a domestic terminal to a quasi international terminal?
Edit to add: Bags would be checked through wouldn't they, if it operates how the
PR department claims it will, Sydney or Melbourne or Adelaide passengers connecting to the London service in Perth, bags would be tagged at joining in the East and so pax would not need to wait in Perth for bags anyway.