Wow - I really think that everyone here is missing the point. Indoor mountain bike parks are lame. Here are my reasons why.
1) For some reason, people have been lording 'Ray's' in Ohio as the pinnacle that any effort in Melbourne might hope to achieve. If this is really the standard that you are aiming for I think the best advice would be to give up now. Did you actually look at the facilities at Ray's? They are designed for 5year olds! There is nothing remotely difficult about any of the 'stunts' and anything that has been built has obviously been constructed by people with little to no actual mountainbike experience (case in point - the 'bermed' corners are ridiculously shallow). If you want this thing to be actual mountainbiking Rays cannot be your business model.
2) So now I'll anticipate the response to my first point from the Rotorburn unshaven masses - "We'll just make it properly and put in cool stuff, it doesn't matter what you (I) think about Ray's (although any response I am likely to get will be sans punctuation)". This point fails for two reasons (though I am sure that there are more). Firstly - 'north shore' ramps are not cool... ever. Secondly, the Ray's business model is such that it relies upon the whole park being easy (lame) enough for little kids and booners so they can make enough money from admissions. People who can actually ride a bike are a minority - and a minority that will see the inherent lameness of attempts to build indoor mountainbike tracks so you can count them out of your costings. If any indoor park wants to make money they will need to make the facilities easy - really easy - so they get the school holiday crowds and corporate groups. Face it - any indoor facility will necessarily need to be lame in order to survive commercially. Just go look at the demographic that features on the Ray's promotional materials - go on, do it. What's that you say? Rampfest is pretty hard and makes money, well, my friends, that is because rampfest caters to a market - indeed an entire sport - that is focused around jumps and park riding. The modern 'dew-tour' essence of BMX is built up ramps and jumps - though even now some purists still think that indoor BMX is lame compared to real trails and street.
Mountainbiking as a sport is centered upon dirt, nature, hills, drifting, technical challenges, steep terrain. Indoor parks cannot replicate this and and will fail commercially if they attempt to do so. Indoor BMX park can be cool-ish, indoor MTB will need to take some miraculous, presently unimaginable, step forward to meet even this lower standard.
I havn't really re-read this post but I hope you get the point...