And with Antony in the strongest position, and Sextus controlling the Mediterranean, Agrippa has to make a deal with one of them it seems-as he surely doesn't wanna get isolated by both people who can completely cut off Italy from their trade and supplies.Very well then, i envisage an empire looking like this;
Rome, Gaul, Italy stay loyal to Agrippa.
Sicily, Sardinia, southern greece and (possibly) his old stomping block Spain goes to Sextus.
Antony retains control of eastern provinces while Africa ( if Lepidus is deposed like i imagine) is divided between Sextus ( Pompeian s still popular their) and Antony.
Thus, Antony is in best poition due to his control of grain and largest part of tax revenue, Sextus controls the Mediterranean trade routs and poses risk to all other parties, Agrippa/senate in precarious position but still have large fleet, army and support, thus making them either a liability or asset to one of the other generals.
Since you mentioned earlier Agrippa was no fan of Antony, and since Antony would be in the strongest position, I can see with that scenario, Agrippa striking some deal with Sextus.