Yes, Persian victory is possible. The Persians were winning most of the land battles. The Athenian victory at sea gave the greeks a navel advantage, which made it very difficult for the Persians to resupply their ground forces. If something prevented the greeks from winning the key navel battles, the Persian armies would have remained well supplied and Persia would have won the war.
Well, after the war, what would have Persia done? Persia had been checked in the danube by the Scythians and in Central Asia as well. I feel that they were at the outer reach of their empire. Would a province such as Greece cost the Empire more than it was worth, much like Britain for Rome?
Keep in mind that the Persians usually appealed to a powerful group within a people, like the priests with the Jews. AFAIK, they had severe problems with the Ionians as they had no clear group to support which could the populace's support.
Well, after the war, what would have Persia done? Persia had been checked in the danube by the Scythians and in Central Asia as well. I feel that they were at the outer reach of their empire. Would a province such as Greece cost the Empire more than it was worth, much like Britain for Rome?
Keep in mind that the Persians usually appealed to a powerful group within a people, like the priests with the Jews. AFAIK, they had severe problems with the Ionians as they had no clear group to support which could the populace's support.
Persia's victory was far more likely than its defeat. It had at this point captured Athens and a naval victory at Salamis for them is surprisingly simple as far as that goes. However if they conquer Greece and Macedon the result is that the policies they adopted to Ionian Greeks get exported further west and eventually the Achaemenid Empire disintegrates for the same reasons the Seleucids would do later: it was too large to maintain with the technology of the time.
Re: the bolded part...Actually I'd have to disagree with you on that. The Achaemenids did quite well for over 200 years, a long time for any empire. The only real problem area they had, in terms of keeping control, was Egypt, and that was largely because the Greeks were actively destabilizing Egypt and supporting any rebels who happened to pop up there (there were other minor rebellions in other places...Assyria rebelled at one point, for example...but they never amounted to anything significant). Had it not been for Alexander coming along, it could have survived for quite a long time more.
In an ATL where Greece and Macedonia have been reduced to satrapies, they'll have even less problems holding onto their subject peoples, most of whom were actually quite content to be ruled by the Persians, who were, for the time, a rather tolerant and enlightened people.