I'm actually experimenting with a butterscotch ester in a beer right now (it'll be ready in two weeks). I started with a Chocolate Oatmeal Stout recipe. I then went to Sugarcraft.com and got a 4oz bottle of butterscotch ester. I'll be adding it in a ratio of 2oz to 5gal, and 4oz to 5gal - I'm splitting up a batch into a few different beers, so I'm only making about 12 bottles of Choco-Butterscotch Delight (6 at each concentration) in order to minimize damage if it turns out horribly (I'll still drink it, but I won't like it).
I'll let you know how it turns out, but I know it's different than what you're looking for presentation-wise. Sounds like you'll have to create your own recipe for that one, but I would err on the side of wheats or heffewizens if you were going to do so. The amber ale might clash a bit with a butterscotch flavor. But what the hell do I know, I'm just winging my own recipe. My advice is really just to experiment with smaller batches until you find a combination you like, then scale it up!