I'm fully aware that I may be alone in this regard, but after the 5th or 6th family I place in Windenburg has to put up with nosy neighbors and their "gift" of fruitcake, it's a wonder I haven't jumped off the roof of my house. And since pretty much every Sim I create is a Loner, well you can see how I might get very annoyed.
"Well, why not just cancel the event?" You may ask. Because I'm not so much of a misanthropic harpy that I don't feel bad for the negative relationship gain and the "I guess we're not wanted here." message that pops up.
So here you have it; a little XML tuning mod that prevents Welcome Wagons from ever happening. Think of it as an override; it replaces a nuisance and gives you nice, cushy solitude.
Tested with both pre-existing and brand new households and saves.