I partially disagree with some of your statements.
There were impoverished aristocrats. That's true. But Catilina was not such an impoverished aristocrat. He was an indebted aristocrat, which is very different.
When I had chosen Catilina as an example, I was so sure, that somebody would pick it up and post that he was not impoverished but indebted.

Fortunately it does not matter! Some roman aristocrats have been impoverished, other were indebted, and some former glorious families have been politically unlucky lately. Other became extreme rich. So the gap widened up amongst the roman aristocracy due to expansion.
Unfortunately, the unwritten standing orders of the roman senate based heavily on the consensus of the powerful
consulares of the big families. These guys ruled Rome, nobody else.
So we have 2 options: we either restrict Rome to the italian peninsula and write a nice novel about the roman republic until 2015, or we live with this dramatic unbalance amongst the roman aristocracy, when this city-state became an empire. But then we have to develop ideas for different standing orders of the senate! The old ones were not longer functional in the 1st century BC.
The civil wars came out of a conflict between members of the aristocracy. That's true. But not only.
There also were deep, long-run and powerful forces that were at work and that made the roman oligarchic regime a fragile building.
You always get my vote, if you argue that longterm processes and structural changes are often dominating over single events. Perhaps you should be more precise about these
long-run and powerful forces, so I can get your point.
The italian elites wanted a bigger share because they felt almost as noble as the old roman nobles and that their local countrymen provided in fact most of the military human resources for the roman army.
Actually, if there was something like a "Roman Revolution" like the scholars of the 19th century claimed, it was the Social War around 90 BC. A revolutionary class, the aristocracy of the socii, revolted against the ruling class, the roman aristocracy, and fought for more political rights and participation. And they won! Unfortunately, this is one of the events during the late republic, which ended pretty succesful. Barely a reason for the Fall of the Republic. It rather prolonged it. Even if the romans managed it lousely.
And the provincial elite wanted to be more fairly treated and not to be at the mercy of a rogue proconsul that could steal them and kill them.
As mentioned above, the integration of the provincial elite was a very urgent issue. But I cant see, how Sulla, Pompeius or even Caesar did more than just try to enlarge their client- and powerbase with their measures. If somebody really started to adress this problem seriously it was emperor Claudius.
There were 2 ways to deal with these challenges : genuine cooperation between highly competent Statesmen or autocracy.
Cooperation, compromise and consensus amongst the (rather not that oligarchic) consulares of the big families during the early- and mid-republic was the key-success factor of the republic, as mentioned above. The key question is: How it could work integrating the real powerful new oligarchs of the late republic?
As far as the idea of some kind of public pension scheme is concerned, it's a good idea in theory.
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The legionary's pay was at the expense at the public treasury. This did not prevent someone like Caesar to decide he would double the legionary's pay when he began campaigning in Gaul.
This could not prevent the generals giving donativa they could finance through looting.
Not just in theory. A clear regulation of pension scheme and pay was one base of the success of the principate! Pension for legionaries was never regulated in the republic and always a start for huge political conflicts. Of course the state payed the quarterly pay of the legionaries. But the real deal were loot and donativa. And this was again fully unregulated.
But in fact this would not change the archaic way of thinking ot the ropman citizens and soldiers.
I guess you mean the roman patron-client system. This is indead one of the major issues of the roman republic. The princeps could solve this problem by implementing himself as a kind of super-patron (pater patriae). But how to diminish, manage or use this patron-client system in a positive manner in a republican system?
The idea of unpersonal magistrates making decisions in the name of the whole political body just was not the roman way of thinking.
Sorry, I don't get your point here.
Augustus built such a system and this did not prevent military rebellions and usurpations.
Slydessertfox already claimed above, that usurpations were the exception until the 3rd century AD. Well, he neglects the dozens of minor revolts until then. I agree, that the principes adopted a lot of right measures, in order to stabilize the empire. But I also say, they failed, latest in the 3rd century. The question is, how could a republic do better and why?