I did it! And it worked! I took Diet For A Small Planet's Spaghetti For Peanuts and made it vegan. It worked beautifully and tasted pretty good.
You can find the original recipe on page 254 of the 20th anniversary edition. For copyright reasons, I don't want to reproduce my veganized version here. My substitutions were as follows: for the margarine I used Earth Balance (note to self: use a different kind of EB. The whipped stuff was kind of greasy); for the low-fat milk I used soy milk (2 cups; worked beautifully and the sauce wasn't quite so heavy); and for the cheese, Daiya.
Now, I don't know about anyone else, but when I have cooked with Daiya before, it didn't melt all that good. I decided to up the temperature of the oven from 350ºF to 360ºF. And instead of baking for 25 minutes, I baked the dish for 40 minutes. This seemed to do the trick; the Daiya Cheddar Style melted pretty good. However, you want to eat this before it gets cold enough for the Daiya to get gooey, because when it cools off, it gets a rubbery consistency. Hopefully the food chemists out there will eventually make a vegan cheese that is a lot more like real cheese.
Results: Well, it tasted good. The peanuts were a bit old; I will use fresh roasted ones next time. Something else I need to do is process the peanuts longer so they are more of a mealy consistency. I don't like them to be peanut halves. And I won't use quite so many of them. (FYI, I did not stick with the proportions in the printed recipe; I added a lot more of everything because we were hungry.) Another thing I'd like to try is cashew cheese instead of the Daiya. Or maybe Follow Your Heart vegan cheese.
In a nutshell: I'll do this again.