IMO ...
Holden centre phase 4:
Open up one of the seating banks inside the Holden Centre. The old glasshouse used to have a seating capacity of 11,000. Minus the deck area, minus areas overlooking the pool, capacity would probably be around to 4,000 per side. That's still a few. Is all the gym equipment being moved out to the new Glasshouse gym? That would potentially enable it. Having seating area for 4000 would allow the club to bring the fans together for occasions and events - eg: watching interstate games: put on a show, create an atmosphere. CFC do seem to be getting into the venue hire business, so this could also potentially provide a revenue stream.
Holden centre phase 5:
Give the joint a lick of paint. It's looking really old and tired on the outside. This would help capitalise on phase 4's potential for venue hire, and also the "Holden Centre" sponsorship value.
Holden centre phase 6:
If phase 4 is successful and bursting at the seams, then open up the other side.
Holden centre phase 7:
Museum in the area where the old cafe / bar used to be ... maybe. As I've written elsewhere, it'd be good to see the club make forever.collingwood.com.au sustainable first before attempting this. I'd also prefer the club run temporary museums for a few seasons (temporary exhibitions are mobile, they can be taken interstate, folks make more of an effort to go to them)