The problem half the time is still getting a protectorate.

I failed to get Egypt as a proetctorate in my game as the Seleucids, I smashed all their armies, sunk all but a few of their ships and had their last city (Petra) and last few troops bottled up and under siege.

I then offered them back all of Egypt, 30,000 denarri, and my extensive map information if they'd become my protectorate.

They refused each time, no haggling, no negotiation just outright refusal. Pontus on the other hand accepted after I took just two of their five cities. Its really bloody annoying too because I didn't want to have to look after Egypt and would have liked a buffer state down there.