Seems to me that you want to be ambitious, but not crazy. The proposed project must be well within the constrains of reality - must be a hypothesis that can be actually tested that is - and must not ignore decades of well-established facts, just to foster some lunatic, crazy-ass idea that one may have. 
 
The flip side to this is that there will be the occasional crazy idea that will be correct (prions come to mind right now, but science is littered with them - viruses causing cancer is another). Probably a simple rule of thumb is that  imagination needs to be based on reality, and must be eventually verified by real experiments!