Hi Giuliano,
The problem with this scenario is that donors and event attendees are not given subscription opt-ins when they donate or register, so we cannot, under any circumstances, use the contacts list as a mailing list. I just don't see how having people sign up to be contacts would be useful. It would be a case of "Sign up to be in our database, but we'll never be able to email you, because we have no way of separating you out from all the people who it would be unethical for us to mail."
If donors and event attendees were given subscription opt-ins, there is the problem that once someone chooses not to be subscribed to blasts, we have no way of contacting them through WA--they wouldn't even receive notices about the event they just signed up for.
Sorry for harping on this, but I've been waiting for mailing list functionality for a long time and it seems like one of the basic functions WA should have. I thought the contacts system was intended to create it. I'd hate to see your development time go into another piece that doesn't really solve the problem either.
Regards,
Paul