We certainly seemed to have something very similar in mind. My recipe isn't a classic Alt recipe, more of a "in the style of" recipe.
The tricks to an Alt, IMO is that it should be malty but dry (I shoot for an FG of 1.008-1.010 from an OG of 1.048), a solid, but not over the top bitterness (I like 30-40 IBUs for that OG), a mild, but noticeable noble hop character. A very subtle roast from a couple ounces of Roasted Wheat or Carafa Special isn't out of character.
1007 is the best yeast, but it is a pain to drop out. I've learned to use WLP011 as a nice substitute, and it drops clear like a British yeast. However, you need to be careful with recipe and mash schedule to make sure it reaches that critical dryness; don't Americanize the OG, use very little to no Crystal Malt, and mash low (149F works for me).
Always good information. I'm going to keep all this in mind and make an alt one of these days. Other summer beers are lined up now but I would think one of these would be quite nice for when fall just starts to kick in. Which around here is in September.