Leading questions:
Representative vs Direct Democracy?
Unitary or Federal?
Presidential or Parliamentary?
How much separations of powers should there be? In presidential systems, such as the United States of America, there is often deadlock between the executive and legislature. In parliamentary systems, the head of government is elected by legislature, therefore, there is practically no deadlock as long as theres is majority support of the executive in the legislature (although, there can still be courts to determine constitutionality of policiss). Would you prefer more checks and balances, but can also result in more deadlock, or a government more easily able to enact policies, for better or for worse?
Electoral method? FPTP? Two-Round? Ranked-Choice/Single-Transferable Vote? What about legislature? Should there be local districts? Single or Multi member districts? Proportional-representation based on votes for a party? If so, how should the party-lists be determined?
Should anti-democratic parties be banned? Or should all parties be allowed to compete in elections, regardless of ideology? In Germany, they practice what's called "Defensive Democracy" which bans any political parties (and their successors) that are anti-democratic. Some of banned political parties include the nazi party.
How easy or difficult should the constitution br allowed to be changed? Majority support or some type of supermajority support?
Should we really elect officials, or randomly select them via sortition?
These are just some topics to think about, you don't have to answer all of them.
Edit: Clarified some things
The quick basics I would want are single transferrable vote (STV), as it has a ranked ballot, regional representatives (important in a large, diverse country, imo), and pretty (although not perfectly) proportionate results.
I would also increase salaries and pensions for elected officials, but on the stipulation that they and their immediate family must liquidate all investments in order to take office, including real estate. The reason for this is to eliminate ulterior motives and reduce risk of corruption, and the compensation of course would be a very generous salary and pension so they never have to worry about their financial situation during or after leaving office.
I would also constitutionally eliminate the ability to take away someone's vote, and to demonstrate why, I'll copy-paste an old comment of mine from my reddit days:
Good explanation, and I agree with your logic. Here in my country there has been some debate around prisoners getting the vote, and given this I can see it iis reasonable to let them vote. In practice it has not been an issue as research shows they often vote against their own interests anyway. Even if they didnt its better not to take the ability to vote off anyone
If prisoners are not given the right to vote, there exists no good reason for them to want to reform. We must encourage the rehabilitation and reintegration of ex-criminals into society else we are doomed to find that they will reoffend again and again.
Treat someone like a criminal and they will have no choice but to act like it.
This reminds me of this board game called Secret Hitler and the game starts with a majority of Liberals (liberal as in non-fascist, not a "neoliberal") and minority of Fascists.
You can even play this online! secrethitler.io (warning, there is a lot of fascist sympathizers on this site, ironically)
Basically, this game simulated the political climate of the Weimar Republic.
There are 3 roles: Liberal, Regular-Fascist, and Hitler (who is on the fascist team)
Liberals don't know each other. Regular-Fascists know each other are and who Hitler is, but Hitler doesn't know anyone else's identity.
Basically, Liberals are trying to enact Good policies, and Fascists are trying to enact Bad policies.
Players can also "execute" another player, removing them from the game. Fascists players can use it to remove Liberal players and acheive a fascist majority and Liberal players can also use it to eliminate the "Hitler" player, immediately ending the game and ending in a victory for Liberals.
It's actually a fun game to play sometimes, and you don't need friends to play it with since you can play it with online people. Although, again, the users on secrethitler.io aren't exactly the friendliest people.
The theme of this game can be offensive to some people, but the creators of this game didn't make it to be pro-fascist, quite the opposite, in fact.