One problem with the standard majority-voting system is this: It encourages factional populations to have more children, so as to win the vote in some number of future generations. Overall, it incites competitive population growth -- which is the very last thing we need, and potentially deadly to our society and the biosphere as a whole.
For example: Demographics in Northern Ireland.
On the other hand, if we "lock in" voting power to certain existing-today sub-populations, then in a few generations as the numbers change (for whatever reason) we will have populations effectively imprisoned in fixed low-voting power blocs. Much like in the U.S. today we are hopelessly trapped by the Electoral College system, instituted to maintain leverage by slave-owning states, and is driving the popular vote more out-of-synch with our Presidential results over time.
I have no answer to this dilemma.