I realized that Terror missions do pop up once a month already, I'd like to have them be even more frequent, but after talking to some people in the IRC I was wondering if this would work instead:
Create a custom mission type that acts like a Terror mission, but instead of having to hunt down every alien on the map, you have to neutralize 75% of them, and after turn 20 or 30 or so, a militia regroups and secures the area, so you can leave without killing everything. I think that would remove some of the tediousness inherent in the normal Terror missions.
Also, after looking at the X-com Files mod, I noticed he used a dummy UFO to avoid having UFO sightings on the early missions. Still not certain how he did it, but I'm new to poking around in OpenXcom, so...