I don't really see Cicero as being able to make much difference in 48 to 46 BC, largely on account of his poor past military record - he had only had one, short command as an ex-consul in the 50s , as governor of Cilicia (SE Turkey, with a mixture of plains, mountains and a pirate-afflicted rugged coastline) and had not done much then. Men with a successful military record and/or a military link like Ahenobarbus, ex-Caesarean general Labienus, and Pompey's sons Cnaeus and Sextus (and their officers and soldiers) would only respect, and possibly obey, a man with a suitable military record and/or a venerable aristocratic family background of generations of past consuls. The latter factor would have helped men like the Marcelli and the hard-line republican zealot Cato the Younger (who was co-commander of the Pompeians in North Africa/ Carthage in 47-46 in OTL and who had led a forced march of Pompeian troops across Libya to the Carthage area so he had shown his military ability and had won his men's support).
Cicero was a 'new man' of socially middle-class origin from a minor hill-town in East Latium, Arpinum, not an aristocratic Rome (though ironically the great general Marius had come from the same town and had also been despised for it by senior aristos in Rome). As a 'new man' with no consular ancestors, and as a self-made lawyer not a general, he was at a disadvantage for winning any aristocratic backing - and there was also a question-mark over his belief in keeping to the law which alienated some senior senators, due to his role as consul in 63 BC in suppressing the conspiracy of Catiline when he executed arrested 'plotters' without trial (probably as an emergency necessity as Rome did not have a prison to keep them in until trial and their friends could rescue them from private houses).Even as the 'man who saved Rome' from the 'demagogue thug and would-be tyrant' Catiline in the early 50s, at the height of his fame, he could not rely on the senate majority (or Pompey) to save him from persecution by Clodius and his populists; by 48 he was a more marginal figure still, and his political revival after Caesar's assassination was a later development and unlikely to have occurred in 48-46. By 44, JC's sole rule and law-bending was stirring up new resentment and all the military Pompeian leaders except Sextus P (exile) were dead, so Cicero had a better chance as a representative of legality and civilian rule - and as Brutus' ally.
The best chance for Cicero was I think later in 44, as a staunch and uncompromising - and articulate - foe of Antony, the new Caesarean strongman and potential army-leader; there were no other strong civilian Senate figures opposing the Caesareans to rival him after the leading assassins of JC were sent out of Italy on provincial governorship jobs, except perhaps Decimus Brutus (another assassin and a respected commander), and the real life senior office-holders like Hirtius and Pansa, moderate Caesareans nominated for the 43 consulships in advance by JC years before, were seen as weak (and ended up getting killed in battle fighting Antony). Cicero could also be useful to moderate senators who did not want a war with the assassins (unlike Antony did) as a link to his protege Brutus , which could be used to negotiate a settlement and rein in 'hard man' Cassius, B's colleague. At this juncture Octavian, aged 18, had only recently arrived in Rome to take up his claim as JC's legal heir and try to take the Caesarean armies off JC's lieutenant Antony, and Cicero and the senate were using him as a way to lure the army and the Caesareans away from Antony. Cicero was the senior partner in this failed alliance, not Octavian - though it seems that both were getting ready to double-cross the other; Cicero's boasts about intending to use and then to dispose of Octavian are recorded so they were probably too open and warned Octavian off relying on him , so if he had been more discreet would he have stood a better chance of winning their clash? Even so, if as in OTL Hirtius et al end up dead, Decimus Brutus too, and Antony is defeated by the senate's army at Mutina and doesn't manage to get away over the Alps to Gaul and come back successfully later in 43 (and join up with Lepidus' rival Caesarean army and then with Octavian) Cicero doesn't have a clear run. Can he use Octavian and/or Lepidus to defeat Brutus and Cassius as he is not a good general himself but then get rid of them , or negotiate a truce with the assassins and allow Brutus (or Cassius too?) without the remaining Caesarean troops turning on and killing him as a betrayer of the cause of 'martyred' JC? It would need a good deal of skill and timing for him to succeed in this and not end up as a civilian puppet of a restored Brutus and Cassius or a discarded unreliable 'front man' for Octavian; he was probably too much past his best to manage to pull this off, and in OTL he dithered too long about getting out of Italy quick when Antony and Octavian proscribed him and ended up killed. (Without that mistake, does he get out to Greece in 42 and later Octavian pardons him and calls him back, powerless, as he did many pro-Sextus nobles like Livia's first husband ?)