Meant to be Sydney CBD 2.0 by 2025-2030 and it wouldn't actually be a bad idea. Parra's starting to reverse it's Western Sydney image to become a economic hub. I know most gov organisations such as ATO/ASIC have large hubs out there, as well as large banks and corps having their second headquarters out there too.
Give it a decent transport line with express connections to Western Sydney Airport, and hopefully connect the light rail to the inner west light rail line at Dulwich hill, and it will boom.
Parra/Western Sydney has 2 missing ingredients to becoming a legit city in its own right.
1 - as you've mentioned, a central transport hub with proper connections to all major corners of Sydney. A direct, no-transfers connection to mascot airport, east, and the new airport and south-west are crucial.
Perhaps a metro link to the new north-west line to provide shorter trips to north-west Sydney and Chatswood too.
2 - cultural and tourist attractions. There's bugger all reason for anyone to visit aside from family and work. It's a pleasant enough place to live and bursting with culture for those who go looking, but on the surface there's not much reason for anyone to stop between Newtown and Katoomba.
There's the footy, Wet n Wild, and a new Zoo opening up.
But Parramatta and the surrounding suburbs lack anything resembling a landmark, there aren't museums or galleries of national significance (moving the Powerhouse is not a good solution), and there's little to draw visitors away from the beaches and bars of the east.
The supposed plans for a Wonderland-revival theme park hopefully come through, would give the west a major point of difference from the Sydney's inner city and could rival the Gold Coast for family attractions.
How about an Olympics and Sports museum in Parramatta or Olympic Park?
An expanded theatre, music, and art district near the Parra Riverside?
A Western Sydney history museum, a Museum of Immigration and Multiculturalism?