I think there may be a chance for serious reform if you look for Federalisation just after the Punic Wars. If we can avoid the destruction of Carthage, but instead see it colonised we see a large Roman Republic with more than a few significant cities, that whilst beaten, are significant to Rome.
I'm not entirely sure how, and I expect it would require the backing of some significant Roman figures, alongside the majority of Italy and territories beyond. But my idea would be
Highest Level - Council of Consuls (say that 5 times fast), with an elected High Consul, or deciding issues on majority vote.
Regional Level - Senate of Cities (Italian Senate, African Senate, Spanish Senate, Gallic Senate, etc) - each city sends a Senator/Represenative to their Senatorial Seat (Italy - Rome, Africa - Carthage, Spain - Seguntum?, Gaul..... Messalia?)
Lowest Level - Each city/group figures out how to represent themselves on their own. Representative of the Lord, Elected Magistrate, Person with the biggest forehead.
Assuming .. 2 Consuls per Senate? The whole alternate years could work with each year a consul is in Rome, representing their region/province, and the other in their Consular seat governing.
The Consuls can either work as a majority voting body, OR every year they choose one of their own as a High Consul - who could have veto, or executive power. I'm not sure. This would likely be where Dictators may have their role, or at the Regional level, superseded by.. Imperators? Or 'First Citizen' (I forget my latin).