As important as progression, is the ability to regress. Project 1999 is a regressed version of ever-quest, the progression servers bring you back to a regressed part of the game. Part of the fun of creating new characters is so you can replay through your favorite zones. In Ocarina of time you are able to travel to and from your childhood and it made the game really fun. Having a Dynasty of characters makes the game fun and re playable. I think Pantheon should enable some type of dynasty system where all your toons are connected to each-other in some way. So when you start a new toon maybe he gains a few perks due to your accomplishments on your higher lvl characters, and in turn buy creating a new class and lvling it up and doing its quest-lines it progresses your dynasty even further. In turn giving perks to your higher lvl characters. And if you own more than 1 account you should be able to link characters from both accounts into the same dynasty. Replaying old content is fun and if you can replay old content and still be progressing your dynasty it makes it even better. Maybe you create an iksar as your second toon and because he is part of your lvl 50 paladins dynasty he starts out as indifferent to most Factions instead of KOS everywhere :) and maybe you lvl your iksar to lvl 30 and because he is in the same dynasty as the paladin, the paladin then gains access to some iksar only quest-lines. The story and progression between charters is endless.
I love this idea! I frequently try to create some sort of RPG reason for my characters to be related (harking back to my TableTop RPG days). Though, I would lean against cross account linking. Though, it would be cool if my friends and/or family members get to share in the same dynasty benefits. However, wouldn't that de-tract from what Guilds are for. Regarding one person having multiple accounts, the main issue I would have with that is there is no good reason to do that other than to "game the system." Either getting around buying additional character slots, trying to play 2 characters at once to collect more resources, and/or get around daily account collection limits. As such, giving them a reward for "gaming the system" strikes me as counter-intuitive.
With the above said, I am not sure how easy to code this would be? Inevitably people might call for selective application of the benefit (i.e. I designate these characters part of my dynasty & these others as independents (probably have to make a hard 1 dynasty per account rule or it would get ugly fast to code up). It might get viewed as an unfair advantage to older players if allowed in PvP (if there is PvP; so probably would not count it there). Though another side advantage of this system is it might help even out zone population.
Over time an MMO's population will consist of more and more higher level characters (who hang out in the higher level zones), which means less people in low level zones (which hurts new players experience with the game). Now the developers of Pantheon have discussed about mixed difficulty content (i.e. putting different level opponents all in the same zone), which is one way to combat this. This idea goes along with that, as it makes it easier for older players to start new characters (who will be little bit different and/or better based on what they already have accomplished). This in turn means there a more players in the low-level zones, and even better experienced players who can help show new players a few cool tricks and pass off tips. Which in turn enhances the community aspects.