Make the akrasia horizon modifiable
Currently, the akrasia horizon (the length of time before which your changes kick in) is fixed at one week. I think this is unnecessary "one size fits all". Not only are there individual differences, there are differences between types of goals for the same individual.
The akrasia horizon represents a trade-off between flexibility and the strength of commitment, but the value of each can depend on the circumstances. Flexibility gains in importance when there is more uncertainty about the near future (e.g. if your goal depends to a large degree on the weather), while strength of commitment gains in importance for more daunting goals (for instance, going to the dentist should probably have a longer akrasia horizon than reading a book)..
One issue is that you might want to be slightly paternalistic about this, given that I get the impression from your blog posts that most people desire too much flexibility. In that case, why not go for a "libertarian paternalism" approach? Make one week the default akrasia horizon, but make it possible to modify it.
Of course, any changes to your akrasia horizon of an existing goal would need to be subject to the existing akrasia horizon.
Adam Mesha commented
Or you could make it configurable, but with 1 week as a minimum.