You hit it right on the head, Heraklia. The Republic had survived for decades, more or less, on its traditions and its expectation that no noble would ever take onto himself the traditional collective powers of the Senate. Sulla's march on Rome with the legions should have been a loud wake up call to the Senate to fix the problem we have been discussing. The Senate might have thought to formalize wages, pensions and retirement lands for the military upon close of faithful service. This might have inspired a certain "patriotism" that could have transcended the ambitions of the generals.

But the Senate did nothing, instead allowing the individual generals like Pompey and Caesar to continue providing for their soldiers. In fact, Pompey had to wait an embarassingly long time after his victories in the East to get his soldiers even the compensation he had promised them. Even then compensation was only obtained after arm-twisting and trade-offs with the triumvirs. No wonder when the crunch came in 44 BCE the Senate could not expect the loyalty of the military.

The problem was made worse after Marius; the ranks were increasingly filled withperregrini("foreigners") who never really shared much in these traditional expectations of the Senate These were men who had no means (and stake in society) except what their generals could provide . It is conceivable that the Senate could have evolved to something fit to rule an empire well beyond the boundaries of the City state, but to do so it would have had to come to grips with certain realities of the last decades of the Republic. It would have had to deal with the reality that by then Rome had something like 16 standing legions (that's maybe 96,000 men at arms) a huge amount of power that was tethered to the Senate only very weakly.

It is my view that the failure of persons like Cicero and Cato to fully realize this point of power politics was the doom of the Republic. The old guard aristocrats were used to thinking in terms of what the few score of old families of Rome could be expected do consistent with tradition and "propriety," but failed to grasp that the Empire had grown beyond that. This empire stretching from Britannia to the Near East depended on military power comprised for the first time of primarily subject peoples, whose loyalties were derived from the more concrete issues(wages, booty, land) and less abstract notions such as "patriotism." It is hardly surprising, then, that it was the warlords as of 49 BCE (or really even earlier) that called the shots and the Senate was simply irrelevant. I think Pompey was the last general who seemed reluctant to break with tradition completely and could have been coaxed into observing the old ways. But things were quite late by 49BCE and his death, in my estimation, ended the Republic's last hope.