All valid points
I traveled the Australind train service a few years ago and found the service rather hopeless (ran more like a School bus) the train even missed a station stop and stopped and backed up to the next level crossing to let a passenger off.
The train was routinely outpaced for road traffic on parallel roads.
The South West line Is designed and set up for freight trains (for the local Alumina processing Industry) the freight trains are frequent but slow moving, high speed trains wouldn't mix that well with them (without Incurring costly curfews)
60 km's of empty landscape could be a feature of the passenger line to Bunbury, for Instance If the track was rated at 200 km/h, that 60 km's could be soaked up In 20 minutes.
Most of Bunbury's attractions (Tourist, Accommodation, Business, Government Services) are located around the CBD Headland and Koombana Bay area, the rest of Greater Bunbury Is mostly Urban Spall.
A second Railway Station located around Bunbury East / Vittoria could accommodate park n ride commuters (keeping their cars out of the CBD)
It all depends on how much money the WA Government wants to throw at such a rail passenger scheme, one thing Is for sure Is that population will continue to grow In the South West Coastal region.
Its WA, things are flexible, miss a stop, back up or use the LX.
As nice as it sounds, no one is going to fund a 160-200km/h greenfield railway across 60km of nothing to a population of 30-35,000.
As for location of station, thats all good but who are most of the people using the train? Surely a connecting bus doing a loop around town as per Gympie in Qld is more value adding. Not sure many people from Perth will be in a need to use the govt office in Bunbury, most is online anyway.
Two stations on two separate branches?
Bunbury will grow based on industry, not because of a high prices railway. The train is to provide an option to get to Perth, yes its used by some commuters but how many billion of tax payers money to encourage people to commute 150km/day to a city in a region of low cost land prices?
Progress upgrades as deemed viable would still seem the better and more practical way to grow. Lakeside to Pinjarra, easy 20-25min saved in one go, assuming no issue for DMU to go through tunnels or suitable other option.
The current freight trains are slow because that's all the funding they need to get the job done. The ~100km distance isn't huge so going faster doesn't achieve alot more.
Google maps says the 97km drive via a road following the same route is 69min average speed of 83km/h.
The current Australind timetable shows Pinjarra to Bunbury at 70 - 74min (depending on the direction) for a distance of 94km, so that's an average speed of 76 - 80km/h with up to 5 intermediate stops, so the train's top end speed must be at least 90 - 100 km/h and its holding that for sometime. Not too shabby. QR manages to keep the RTT up to 120 (used to be 150) km/h sharing tracks with 26t/axle coal trains. So maybe part duplication to help prevent congestion and enable more services.