What do you do with a potential Federation member who is peaceful prosperous, the people are educated, well fed and happy yet they have no concept of democracy?
Say like a royal government system (planet Brunei
), or a communist government system (planet Bolshevik
), or a corporate government system (planet Microsoft
)? But with the addition of all
the things you listed?
If inclusion of that world is to the existing Federation's best interests, then sure.
For all we know, planets with a democratic government system are a minority within the Federation.
Do you totally upend their culture to let them join or let them select their representatives by some other means?
Upend their culture? I would say no, take them in as they are, or reject them.
Even with a democratic planet, the representative wouldn't necessarily be select by a election.
What if it's ritual combat to the death?
If the traditional form is single combat to the death for the privilege of being the planet's representative (or one of the representatives really), then that's their business.
Any society which lacks democracy will inevitably be dominated by a ruling elite who dominate and oppress the masses, prompting anger and factional conflict.
Unlike in America, where we have democracy?