I like the idea, but it has a few problems.
1. Plenty of other people probably have had their minds wiped at some point, but those two specifically having their minds wiped likely does have some signifigance. All the same, that isn't much to go on.
2. America is a fairly wealthy country. There are a lot of rich people, from a lot of different places. I think it's a bit of a stretch to assume that anyone with a lot of money in Gravity Falls has to be from the same family.
3, It's entirely possible that the author first noticed that there was some sort of government cover-up. From there, he could have discovered that it was related to the founder of Gravity Falls, and continued from there.
Personally, I'm leaning toward the idea that the author is a character that hasn't been introduced yet. Most of the evidence up until now pointed toward McGucket, and since that's been disproven, nobody else really matches up with the evidence.