Doesn't seem TOO bad an idea, for it all. An AU game would be interesting to see. Let me give you a bit of advice, though. RPG Maker VX Ace is harder to use than it looks. I've had my copy since... bit before April. It's POWERFUL, but if you don't have much of a talent for designing game maps on the fly... it's going to be a bit of a pain. Also, forest decor is a pain in the ass. Same with City Decor, City DESIGNING, etc. etc. etc.
Then there's the fact that you have to program in EVERY little detail for animation so the fires look like they're slowly moving, and you start to see the problem. It's a WONDERFUL tool, but you have to be dedicated and keep yourself up on it to work well with it.
I'd reccomend taking it down to two routes, if possible, until you're used to RPG Maker VX Ace, or even building just a single route to see if it's feasible.