I think the weekly post idea really applies to the reader, not the writer. Perhaps you could get around this with a "digest" style of posting. I.e. I can write as many posts as I want, but it will only be published once a week as a digest of posts. This might fit better with human behavior too as it lowers the cost of a single post while still achieving the goal of updating friends on what's happening at a spaced interval.

Anyway, love the idea. Good luck!