In accordance with the 2004 BJCP Style Guidelines, a mead made with maple syrup would be entered into the "Open CategoryMead" style (26C). Yes, you could ferment a maple syrup / water delution (you must delute the maple syrup or the yeast will not ferment it, as the sugar content is too high) but that would Not be mead.
I would be interested in the flavor of a "maple only" brew, but believe that the yeast used would have a large impact on the flavor. I would not say that the flavor would be "nasty". To see what you might get, try mixing maple syrup with some neutral sprits (Vodka, Everclear). The flavor and aroma of the maple should be present, but with more sweetness than you would have if you fermented the maple syrup to make the alcohol.
The real problem that I see, is getting good maple syrup at a reasonable cost. Here in the West, pure maple syrup is expensive. To make a 5 gal batch at an original gravity of 1.085 would require about 10.75 lbs or 3.5 quarts of syrup. That would be in the neighborhood of $35.00 for the syrup. That is what I pay for a 55 Lb sack of base malt! Perhaps a small 1 gal batch would be a good place to start if the initial flavor experiment tastes good?
I've heard talk of adding maple syrup to beer, but what about just maple syrup and yeast? Should work, right? Nasty?