The interesting question about this alternate history with the great republican Cicero is:
- what were Ciceroes thoughts about the weaknesses of the republic?
- did he recognize the structural deficits of the roman society, which leaded to the paralysation and desintegration of the republic?
- how would he try to reform the republic?
- is a working and stable roman republic possible at all, under the given circumstances in the 1st century BC and how could a republic cover the needs of an empire?
In order to answer these questions we need an insight dicussion about roman society, constitution, political duties/processes and civil/military administration. I doubt, Cicero or anybody else would have been able, to reconstitute the republic. But perhaps this is not your goal at all and at the end, it makes no difference, if Cicero dies or not.