You could have an actual pumpkin beer, and I've brewed them for years. Make a wheat beer base, to provide more texture for the beer, then chop up a pumpkin and a small hubbard squash. roast them in the oven and add to the mash.

If you want, you can add small quantities of the pie spices, but really, the caramelized pumpkin/squash will give a lot of flavor.