I realize I'm in the minority, but personally, I'd go for it. If you are somewhat familiar with SEA and do not have any mobility restrictions, I think you'll have an extremely good chance of making this connection. The early morning Horizon flights have a stellar on time rating (>95% for AS2328, according to flightstats), and more often than not they land ahead of schedule. So long as you walk quickly and directly to your next gate, 40 minutes will be more than enough time.

My vote is, take the extra 1.5 hours of sleep at that time of morning!!

P.S. Yes, AS has the official policy of requiring passengers at the gate at T-30. But they can also see that you're on a legal 40-minute connection from another AS flight. There is no way they would offload passengers in that situation, it would be a PR nightmare! So I don't think that's anything to worry about, until maybe T-15 or later.