I know a lot of people get quite annoyed over some certain embassy collectors at times, those who persist sending requests even after you've repeatedly denied them. I understand that the 7-day buffer was put in place most likely to help prevent this, and I really don't know what we'd do without it, but I think it may be convenient to take it a bit further.
What I'm suggesting is that sending embassy requests after repeatedly denied by the recipient (say, after three denials in the period of six months) should be considered a form of spam, or if possible, stopped by game mechanics altogether. I know, for me at least, it would make it a lot more convenient for embassy collectors to be prevented from spamming my regions whenever they can, and simply creating new puppets when they get banned.
Just something to think on.