I think Dreamworld needs another major thrill coaster, maybe something more airtime focused.
I don't know much longer they can keep Gold Coaster going for, but after Steel Taipan, there really isn't much else on the coaster side.
I would love to see an RMC personally. But really anything I would be happy about.
I don't think they should remove moto coaster completely, as much as it's a bit awkward. I think they should just retheme the ride completely, renovate the station, non-prototype trains (regular bike ones), and just make it a lot prettier. Sure it will be a boring coaster, but it will be comfortable, and not everyone who is slightly larger will be turned away.
That's really all that I think needs to be done immediately. I think the family's already have so much to do at the park, that I think they can focus on more thrilling attractions.