I've had very similar ideas in the back of my head for the past year or so. Some thoughts, offered humbly:
Make sure you have a corporate structure that legally enforces your principles and governance system, as well as the rights and responsibilities of your users/members, and publish your founding documents (articles of incorporation, bylaws, etc.) so people can verify everything. As I'm sure you're aware, too many user-generated content ventures start with assurances that sound great but end up being sold off and shut down or otherwise exploited. Legally bind yourselves from doing that and I'll be more likely to participate.
For governance, consider alternatives to one-person-one-vote like quadratic voting (glenweyl in that thread is the guy who came up with it). The basic idea is that when you hold a vote, people spend a virtual currency to buy as many votes (N) as they want at a cost of N2 units of currency, and when the vote is over, all the currency spent is redistributed equally to everyone who voted. For example, if I feel strongly about the subject, I can buy four votes for 24 = 16 units, but I can be outvoted by five people each voting once the other way and collectively only spending 5 units. Afterwards, I and the five other voters all divide the 21 total units spent equally, receiving 3.5 units back. I end up netting -12.5 units while everyone else nets +2.5. There are heaps of academic papers working out why this is efficient, which in a voting system context means (I think) it maximizes satisfaction and minimizes disappointment. People who don't care will vote randomly and balance out, people who care a little can vote a small number of times in their desired direction based on how much they expect to get back, and people who care a lot but might be in the minority still have a chance of winning by voting a lot.
In your case, you would issue a set amount of currency to each user account when they register. To prevent gaming, you would want to limit voting to accounts that have paid for a membership (gold) and/or have maintained a certain level of positive activity on the site, as well as things like not letting a user participate unless their account predates the proposal of the vote. (I believe part of the system is that whoever proposes the vote has to commit their votes up-front. There are probably other subtleties to watch out for.)
I think your community will live and die based on its content policies and moderation system. I have a lot of thoughts on the subject, but I'll try to limit myself.
Make the tough decisions about allowable content as early as possible. With your ambitions as a global site, I don't think you can afford too heavy a hand when it comes to speech, so it's difficult. Would you allow creepshots or coontown? What about call-out communities like ShitRedditSays or TumblrInAction? Gore? Porn? Nudity? Doxing? Gossip about private individuals? Making fun of what people say on other sites? How do you distinguish making-fun-of from laughing-along-with? The difficult reality is that human beings crave interpersonal drama and other unsavory but stimulating things, so a site bereft of all that might never grow the way you need it to. If you can address the unsavory content question with a simple principle or philosophy (8chan's is "anything goes as long as it's legal in the United States," but you probably don't want that), you'll prevent a lot of confusion and strife later.
Have transparency and due process for users in the moderation system. I actually think the suggestion of electing moderators indicates that you've put some thought into fair moderation but have arrived at a local maximum. Seek inspiration from functioning real-world legal systems instead of simply adding democratic elements to the online community status quo.
Current systems are inherently dictatorial and incite moderator-user conflict because they bundle the functions of law enforcement, legislation and adjudication into the single role of "moderator" (or in the case of reddit, moderators plus the super-moderators called "admins"). Mods make the rules and enforce the rules, and users have no recourse. Better to have specific rules with specific consequences and allow users to appeal charges or "plead guilty." Evaluate appeals based on the limited circumstances involved, not the personalities involved: did this post violate this rule, not "Is this user a bad person?" If a conclusion can't be reached, let the post stand and/or put the rule up for revision.
Users should define the rules democratically; moderators should enforce them. Consequently, being a moderator isn't a position of power but a position of servitude, so electing moderators doesn't make sense. Moderators should simply be volunteers, and if that's the case, why not just make everyone a moderator? With the right system, you can.
If everyone's a moderator, your rules have to be designed for objective interpretation. "Refrain from abusive comments" can't be evaluated objectively because "abusive" encompasses a spectrum of behaviors where differences of opinion at the border are inevitable. "Refrain from name calling and insults" is much better. For another example, reddit's recent guideline of "Refrain from behavior that might make someone feel unwelcome or unsafe" is bad for many reasons. Good, enforceable rules in an online community can't depend on the feelings or characteristics of the users involved because those feelings and characteristics can't be verified. Good rules can't rely on the ability of the individuals subject to them to predict the future or the way other individuals are going to react. Rules like that are ripe for selective enforcement and can be abused to shut down legitimate disagreement.
Besides rules that can be evaluated based on objective facts, you need to prevent moderation war (like "revert wars" on Wikipedia). I think it's possible. Moderation is a privilege that can be revoked, just like posting. When a user is subjected to moderation of some kind ("Post removed for violating rule X"), that user should be allowed to appeal. Ultimately, that appeal should be evaluated by a quorum of users voting on the original decision as well as whether the moderator acted in bad faith. If you're found to have moderated in bad faith, you lose the ability to moderate for some period of time. On the other hand, if it's found that your appeal of a moderator action was in bad faith, you lose the ability to post for some period of time. Repeated offenses result in longer periods of reduced privilege.
Wikipedia has a system where one editor can bring another editor before the Arbitration Committee to accuse them of violating some part of the alphabet soup of Wikipedia rules. That system approaches due process, but it's all based on making edits to special Wikipedia pages in ad hoc ways. I believe a system like that can be systematized to remove individual power and influence, as long as the rules are defined in a way that allows for objective evaluation and pre-defined "punishments."