Ooh an Aussie BBQ/Bar with verandah, either over looking the end of the rapids ride or taking over the old Sky Link station, I like!
I'd like to see what ever happens to Eureka Mountain happen, wether it's re-opening the ride, gutting the mountain and starting again, or demolishing the mountain and putting whatever there. Throw in a few small elements to Thunder River (particularly more ways to get wet) and I think that's concept enough.
I also think expanding Gold Rush Coubtry to include the old Blue Lagoon site is a waste of a big plot of land. For my taste I'd like to see Blue Lagoon's plot of land be given a dark sinister theme. Something like X-Sector at Aton Towers would fit the bill nicely. You could easily open it with one coaster to start off with too and grow it over time.