It's not perfect by any means, but the system used by the English football team I support (Tottenham Hotspur) for cup finals and important away games etc is one that rewards the fans who have supported the club during the year, something I would have thought the Seahawks would want to do for the 12th man.
Each match you attend is assigned a points value, say, 10 points for less appealing games like League cup games against Grimsby, or 1 point for the games everyone wants to go to. The lack if NFL games would make this less practicable, but I guess there could be tiers for pre-season games, then the likes of Jacksonville, and then the niners.
You accumulate points over the season and when the big games roll around you apply for tickets, with the people with the most points being successful. This means that season tickets holders and anyone who goes to multiple games are rewarded. Everyone who wants to be included in the scheme pays about £40 per season and gets a swipe card (and first dibs on all tickets) which, in this case, could be used to make sure you get the points if you buy the tickets via the secondary ticket websites. I think you could give season ticket holders first right to buy, then those with the most points get the rest.
Look after the fans, Seahawks!
Edit: looks like the message above shows that they might be doing something similar. Excellent, if so.