It's interesting that the main thinkers listed are all Roman. They're definitely the best known, but Stoicism was a Greek philosophy first and foremost, and Cleanthes, Chrysippus, etc. were more significant than any of the Romans.
Stoicism had a lot going for it, but it was also full of a lot of crazy nonsense - there's a reason you've never met a Stoic who was fully on board with Stoic natural philosophy or "physics." The logic eventually made a comeback (via Frege, possibly due to plagiarism!), and the virtue ethics got absorbed into Christian moral philosophy by about the 13th century (by way of neo-platonists who influenced Dominican philosopher theologians like Aquinas). It's not surprising that it ran out of steam.
The 13th century seems like a late stoic tributary to focus on — some stoicism seems present in the gospels.
Imagining better systems before doing that is just a form of xkcd’s nerd sniping.
And the biggest challenge to representative government might well be that most people are terrible at engaging it productively. Voting is the bare minimum and most people don’t vote (let alone organize and lobby effectively). Some significant portion of those that do vote can’t correctly draw a line between policies they’d like and candidates who intend to work on delivering, and that’s before we get to the portion of the population that may not correctly anticipate policy outcomes or even really understand policy as a concept.
The system has actually been functioning surprisingly well considering, and as catastrophic as recent elections could be seen as, the outcome arguably represents a reasonable degree of fidelity to the input from the electorate.
If we still hold free and fair elections, the task of those who want representative government is to change enough of the electorate first.