Onya Dude ... for taking the steps to highlight to council the needs of the community. Would definately travel out for a dedicated facility.
In terms of community support ... and as a suggestion, have you linked any of the comments / actions etc from the RNP MTB plan from a few years ago ... ie, I remember there being a fairly large body of work by locals highlighting community interests ... including track day volunteer programmes etc ... which unfortunately was ignored or not allowed by NPWS. (something related to all track work must be by NPWS employees). Given council doesn't have similar regulations (assumption), this community (both shire and Sydney MTB in general) volunteering program would give a bit of weight to your proposal.
Anyway, good luck and will definately be joining the club shortly.