This "balance" you're speaking of only benefits the duopoly that's developed BECAUSE of the FPTP system.
Organizations are like organisms. Organisms don't only have to replicate their DNA to be successful—they also need to replicate their environments (e.g. buffalo and elephants protected grasslands from being overrun by woodlands, pine forests making wildfires more common, etc). In this case these parties both have disproportionate power because of FPTP and are both interested in maintaining this "balance"
sorry for the self-plug
Maybe I will, but I've had this update pending (see preview here[0]) that adds some major algorithms that any self-respecting voting theory nerd would expect to see. I started my first software job right as I was wrapping that up though and never fully got through with it. Maybe this winter break I'll have time tho... I'd like to have that update out before sharing it more loudly
That's a very long-winded way of saying "some people's votes are weighted more than others", which is an inherently undemocratic principle.
Different voting mechanisms, along with federal systems, are a way of balancing those competing concerns. They allow you to form a larger body politic that would not necessarily be willing to be bound together in a simple “majority rules” system.
Has there ever been, in the history of human civilization, any self-styled democracy that did not weigh the votes of some people more the votes of others? Whether by sex, gender, race, wealth, education, criminal status, party membership, age, or status as an elected official, I'm pretty sure every single democratic state has continuously subscribed to some non-uniform distribution of vote weights.
With modern technology, it maybe possible to create a truly direct and equal system where newborns have the ability to ratify trade deals, but this might not be desirable.