Roleplay it. Let the AI automanage those cities without governors. Don't try to optimize everything.

I'm playing a Roman campaign as well. It's 196 BC and despite my best efforts to play it slow, I'm now fighting all out wars on all frontiers except Africa. The Lusotanians, Sweboz, Epirotes and Macedonians attacked me more or less at once.

Fortunately I had around 500,000 in the coffers, which enables me to strike back. Though I didn't really want to do it, I now control most of Spain and will have wiped out the Lusotanians in the next 5-10 years. The Sweboz are also hard pressed, and the epirotes are losing town after town in Greece. My only real concern if Macedonia; a behemoth that so far has only sent a few stacks against me. Unfortunately they have refused every peace offers so far.

I wonder about one thing though: My faction leader has finally gotten 2 stars in command and management; he is also a populares. Shouldn't that mean the Marian reforms kick in?

rgds/EoE