I'm new, as you know, so take with a grain of salt, as you will.....
1. The top 500 (random number, enter number there that you see fit) miners in the last 30 days or X blocks should be able to vote. Same people are the only ones able to submit ideas to be funded.
Their economic incentives don't always align with the best directions for the development of the coin. Also they may be deficient in technical understanding of complex issues.
I guess you will always have both those problems with any kind of fairish voting system.
Another 2 options:
1 - Allow the development team to (heaven forbid) pre-mine some coins for themselves, they get paid when they make them worth something
2 - A perfectly fair launch with no treasury system and the developers beg for a different currency to fund development (USD, Bitcoin). People have incentive to fund good development as it will increase the value of their holdings. This does obviously means that people that hold the coin but dont help with funding the development get a "free ride".