GO FOR IT!
An all maple design with a quality spruce top and an ebony fretboard will be fine. The sound of an acoustic guitar comes mostly from the top and the construction. The general theory is to have the ONLY vibrating parts to be the strings and the top, while EVERYTHING else remains inert. Experimental guitars have been built without backs to prove that the tone comes from the top. They of course lacked volume, but they made the point. Now while the necks, sides, and backs of acoustic guitars will inevitablely vibrate, the goal is to keep it at a minimum. The concept is for the strings to transfer maximum energy to the top, and for the body to reflect and project the sound of the vibrating parts. This is the master skeleton key to great tone and volume in a superb acoustic, and Paul "Wonka" Smith has caught this drift. All the factors do come into play, so don't misunderstand me. All the woods interplay together. However, for acoustics, the neck material isn't as important as it is in an electric, or in a banjo for that matter. I'm speaking in general theortic terms, and opinions vary vastly. Some combinations work better than others. For example, someone with more experience than myself won't use a maple neck, or body on an acoustic unless they are paired together....and that someone is Bob Taylor. The bottom line is that some things work well, some things don't, and some other things work magically. Maple would doubtlessly be beautiful, and, in my humble opinion, would sound extaordinary with a quality spruce top. I would totally go for it!