Base Max/Min Rank requirements on the user's history across accounts, to avoid circumvention using alternate accounts
Of course, this is one of those 'easier said than done' things, so bear with me - there's a bit to it.
This comes out of the recent forum discussion where a player rage-quit while alleging that his 'beginner' game was infiltrated by experienced players.
While I'm not sure that the player in question was necessarily right under the specific circumstances of his game, a few points emerged in that discussion:
(1) It is both permissible under the rules, and common practice, for experienced players to maintain 'alternate' accounts, at least for the purpose of play-testing strategies and game mechanics.
(2) It is not uncommon to find experienced players, via their alternate accounts, entering into beginner games that their main account would not be eligible to enter.
The problems with this 'sandbagging' are myriad. While there will naturally be a wide range of skill levels among players who are new to Nu, there are good and valid reasons to bar experienced Nu players from beginner-only games - hence the existence of the 'max rank' setting in the first place. But with the availability (and legality!) of alternate accounts, the 'max rank' setting is pretty much meaningless. A reigning emperor could enter a beginner game with an alternate account, and not only would the system permit it, but it would be 'legal' under Nu's current rules.
I can only assume that there are other problems with each player having multiple accounts, as well - difficulty in tracking user metrics for site development purposes; it devalues the premium membership by providing a legal workaround to the game limit; etc.
The solution here is tricky, and there are a few options, but here's what I think is likely the least onerous in terms of modifications to the system architecture:
Require all users to register a (for lack of a better word) 'global' account, and merge all existing accounts underneath the global account as discrete 'profiles' - with merged accomplishments, at least for the purposes of determining eligibility to enter games. Each player may only have one account, but each account may have several profiles - probably a limited number for non-premium members, but a larger number for premium members, to facilitate legitimate 'play-testing' purposes in private games. Ideally, you would have one login to your account, and could easily access any of your profiles therein.
Obviously, enforcing a one-account limit would be a separate challenge, but it seems unlikely that many people would actually violate the site rules simply for the purpose of 'sandbagging'.