Veterans should start at a higher level than people who just reached 30 in the new system.
- Player will experience the "rush" of leveling together regardless of how much of a level difference there is between them because that difference doesn't effectively keep them from playing together (unlike in a game such as wow). So you can't justify not giving veterans a level advantage on the basis that the level difference would have a deleterious effect on the game.
- Jumping a player to 200 doesn't diminish his fun because there are always more levels and more rewards. Free stuff isn't unfun. So you can't justify not giving veterans a level advantage because it would be just as much fun climbing from 300 to 301 as it would be to climb from 30 to 31.
- Tailored rewards are going to be tailored by an algorithm anyway, and there is no reason why you can't tailor a person's rewards with that algorithm right now by processing games played retroactively. So you can't justify not giving veterans a level advantage because they wouldn't be able to have tailored rewards.
- There will always be people who can't catch up because some people devote more time into this game than others. That is true now, and it will be true 4 years from now when people have level differences of more than 300. So you can't justify not doing giving veterans a level advantage because it makes it impossible for some players to catch up.
- Exclusive emotes are literally impossible for some players to earn (definition of exclusive), and are less appealing to veterans than the rewards that come with being higher level and the posterity of a number that represents their commitment (accurate to within several games). That means exclusive rewards feel bad to people who won't get them and feel worse than the suggested level advantage alternative to people who will. Your most dedicated players are actually experts on the subject matter of "what feels better to dedicated players"-- so listen to them.
