I might try a fusion of light molasses and dark corn syrup--both offer the sweetness and consistency and liquid.

I would add a liquid, such as one of the other suggestions. Fruit juices that contain only fruit are also good additions to quick breads. (I use apple or orange juice quite a lot.) I would also add about 1Tbls molasses. This will darken your bread a bit and add a nice background flavor that should make up for the lack of maple flavor.

I bake a lot of sweet breads and muffins using maple syrup and to me nothing will take its place, but you can use honey or agave as a good substitute. If you don't want the bread any sweeter, I would go with milk and add in the maple extract if you would like that flavor. Buttermilk, especially whole, is a good addition to quick breads.

I would lean towards honey or agave nectar rather than applesauce. Applesauce is very acidic and can change the texture of your baked goods.

I think the liquid is important. I would add the same amount of honey or applesauce. The apple sauce would be less sweet. You could cut the sugar to 1/2 a cup and use honey.

if you're in an adventurous mood and you have potatoes you can try this - http://www.choosingvoluntarysimplicity.com/mock-maple-syrup/ (I've always meant to and never got around to it)

I found the full recipe online:
http://www.bostonmagazine.com/articles/recipe_cranberry_maple_pecan_breakfast_cake/

It's the Cranberry-Maple-Pecan Breakfast Cake from Joanne Chang.

And if you change your mind and think you need a bit more sweetening power, a tablespoon or two of brown sugar would not go amiss with aargersi's suggestion.

I would go for something with moisture I think, though quick breads are pretty forgiving ... what are the other flavors? Milk would be good, maybe juice of some sort that goes with the other flavors, even yogurt or mashed banana would add moisture. The dairy products of course also add fat - which I think is a good thing. Hmm - what about a couple drops of the maple extract stirred into 1/3 c milk? That's what I would do ...