All these ideas sound good and all, but closing the park down for anything more than 3 months, spending hundreds of millions of dollars on completely changing the park, and then changing the name sounds like a fantasy. Yes the Dreamworld name has some dirt on it since the unfortunate event, but it also holds nostalgic value.
The only thing i think Dreamworld needs is some proper investment and care.
What i'd do with Dreamworld is work with what you have. So unfortunately MDMC will be staying.
Also bring back something on the lines with Dreamworld Insiders, it'd probably have to be a new cast, but it will be a lot of fun.
Trying to keep rides a float for a long period of time is the first thing i would do, and then build a RMC Hydrid, to gain some more guests.
I also really loved the idea of nostalgic advertising, it would be really neat.