First, let's start with research. For Science of course.
We can't take any strong flavours or styles. Stout is right out the window, and anything with too small of flavour or body isn't going to hold up it's malt to the spice and pumpkin. Let's toss out most lagers, blonds, and pilsners. I gravitated towards an Amber. Selecting Crystal 60 to provide color, and some caramel flavor. Victory, a Pinch of Chocolate, and American two row to round out the malt bill. Add to that a bit of dark brown sugar and maple syrup and we've got our fermentables. For the Hop schedule, Liberty on the bittering, Golding at just before flameout. Mostly to provide a nice spiciness and aroma.
And that leaves the all important part. Pumpkin and Spice. I personally like pumpkin spice, so investing in fresh spice to grind for a batch seems worth the investment. I made my batch already by combining Cinnamon, Ginger, allspice, cloves, and nutmeg. You can find plenty of recipes for this online. For the pumpkin, I prefer canned. Processing raw pumpkin is just too difficult to make worth your time. Add spice to taste, 1-2 tablespoons should be sufficient.
Personally, I'm going to route of Pumpkin into the mash. You get the profile desired, and it's one less step than trying a pre-boil. Ofcourse it adds difficulty to the Sparge. I'll ferment on WLP 060, a nice rounded yeast. That will help keep a mellow profile. Here's hoping the fermented result will be interesting.