Rhodes is always a bit of a plum -- and does not seem to draw too many counter-attacks unless Macedon is still active. Egypt is the only other faction I've seen try for it -- and I suspect you'll be keeping them busy elsewhere no?

As to keeping Egypt at bay, you might consider a series of coastal strikes using your fleet and army. Hammer and cripple Alex, Jeru, Sidon, Antioch, and Salamis (esp if you've got onagers aboard for instant attacks) in a series of strikes over about 8-9 turns and then take Rhodes afterwards for rest and refit. And by strikes, I mean take, enslave (extirm if you do that), raze buildings and up stakes. You don't care if you're creating multitudes of Eggy peasants and you get to support the People's Front of Judea into the bargain. This should slow them down a bit, but not strap you with the take, conquer and rebuild stuff.