CK3 Roman adventurer

With adventurers, I have this idea that it would be fun to start as a Roman Hellenistic adventurer and reform the Roman Empire, but I seem to get stuck midways.

I usually travel around and upgrade my camp, adding men at arms as I go along, and then at some point you can use the adventurer CB to invade a region and take over, convert the counties to Roman and Hellenistic.

In a couple of tries I've done this in both Northern Italy and on Sardinia and Corsica, but the issue is... You're so behind in tech that your men at arms can't be upgraded much, and everyone and their mother will start to declare holy wars against you once you reach a certain size.

Got any tips on making it bigger than, say, owning Corsica, Sardinia and Sicily?

The one idea I've had is to join the Byzantines, but then the emperor immediately starts to convert your counties to orthodox...