Beware of the big length, but this would be an ultra-long term plan if I had the budget of Chinese theme park companies. My idea is that Dreamworld would engage in banking on the recognition of the park's history and reintroducing former rides that were popular with guests, as well as introduce new flashy rides that aren't seen anywhere else in Australia. Most of the actual theme park section, especially the thrill would need to be wiped clean and totally replaced. Tiger Island, Corroberee and WWW are mostly left untouched with a few cosmetic upgrades. There isn't exactly much worth saving beyond those at this point.
Things I'd change right away (short term)
Change to seasonal operation. This is done in a similar manner to Adventure World as theme parks usually don't perform well in the winter months. This allows the park to make additions and changes in the winter months.
Lower ticket price to make DW a more cost effective alternative to MW.
Rocky Hollow is rid of its stupid modifications and replaced with seatbelts like every other log flume ride.
Areas I'd work on in the medium term (1-3 years):
Wipeout replaced with ABC Rides Torbillon. Identical name and identical theming to the original, promoted as a next generation retro revival. This is because Wipeout is one of the more iconic and popular attractions Dreamworld had and keeping the Wipeout name will draw the attention of guests. Having a flashy ride like this will also grab plenty of press and public attention due to its unusual nature.
The former Thunderbolt site that was to be replaced with the lazy river is replaced with an RMC Raptor, named Thunderbolt after the original. This allows the park to retire TOT and having both of this happen in the same time distracts guests from TOT being closed as there is a new coaster in the park to ride instead.
Tower of Terror is closed, and Giant Drop is converted to a Falcon's Fury gondola. Ripping down the TOT will free up space for another family ride in Dreamworks Experience.
Areas I'd work on in the long term (3+ years)
Hot Wheels Sidewinder replaced with a waterslide tower. WWW don't have a Boomerango or a Six Flags-style King Cobra waterslide so maybe it's time to get one of those. This essentially completes WWW. If you want to do a direct coaster trade, an S&S 4D Free Spin would be nice, but HWSW's plot is better for a WWW expansion.
Dreamworks is expanded. The arcade and Kevil Hill are demolished and replaced with a Croods or How to Train Your Dragon area, including a couple extra family flat rides.
Gold Rush is fully rebuilt with the same theme in mind. Plans for the ampitheatre would be scrapped. A dark ride and a new family flat would be built in this development. Buzzsaw is kept and refurbished a la Wipeout and given proper theming. Gold Rush's initial expansion is targeted as a family thrill area, a step up from Dreamworks but not as intense as the rides in Ocean Parade, that is until...
Tower of Terror ultimately replaced by a new marquee roller coaster in Gold Rush and covering up to Blue Lagoon. A Mack multilaunch or Gerstlauer Infinity Coaster would be nice for this area. If you want to really go off the shelf with this, a clone of Smiler would be a cool addition.