I just tried a Persian game on Monarch and had a fairly similar experience. I came almost close to the land but ultimately failed somewhat spectacularly.
Babylon is obviously the first target; and with the extra 4 immortals from them declaring war I made fairly short work of them. I got lucky: they didn't have any spearmen, and there were 3 bowmen in Babil and only 1 (!) in Ninua. Ur was another matter; they hired an Impi mercenary so I didn't take that until long after the rest of Babylon and India had fallen to me.
India had a handy three cities which fell rather quickly, and by the time I had finished with them I had also razed the barb cities in Anatolia and resettled at better sites. By then the plague was ravaging Egypt and Greece, but not me, by some fluke. So as soon as the immortals were in position I seized Egypt fairly effortlessly, although I didn't quite grab Abdju (and never did). Greece was harder: after a few immortal rushes Athens fell and the civ collapsed; but I never took Sparta because the region was so remote. I also had to found Byzantium on my own; the Greeks were playing a sloppy game.
However, that's where I stalled. Up to that point, I had succeeded entirely on massive Immortal rushes primarily starting from Shush, Nineveh, and Babel (Parsa was churning out wonders and spearmen to protect from the upcoming barb threat). However, by then only Rome and Carthage remained in the West and both were too strong and too far away to conquer without an actual balanced army--which moved too slowly to afford.
By this time I had made a few other mistakes--I had researched Theology instead of something actually useful, and hence had four holy cities (Delhix2, Jerusalem, and Artacoana, the barb choke point). Of course, because I had Delhi churning out wonders instead of temples, I never ended up with ANY great prophets. Whoops! Too bad, because they could have saved my economy.
My land at this point was largely undeveloped--I had a strong road network and vital resources were hooked up, but no city was at its full potential; I was too busy barreling ahead and conquering. I knew this would be a problem eventually, but hoped that I could reach my goals before then. But no. When conquest stalled after taking Athens and Egypt, the economy, sustained almost entirely by plunder, began to hemorrhage. I was losing about 50 to 70 gold a turn, and even with a 700 gold war chest that doesn't last long.
Bankruptcy ensued and the army gradually died off. At this point I began to focus on saving the economy and building wonders (particularly Colossus, Artemis and Lighthouse). Nothing was enough.
Eventually the plague hit and ripped me apart. It was all I could do to hold the barbs off Egypt and Samarkand, and eventually I couldn't do it. I lost Delhi (obviously a core city) and hence had no chance.
<b>BUG</b>Barbs took Delhi, but as soon as the resistance ended, the city IMMEDIATELY flipped back to me. I was happy until I noticed something: ALL of its wonders had disappeared. Oracle, Parthenon, Artemis--all gone forever. Any idea what happened?
I hung on until 550 and then switched to the Vikings.
Since then the AI has held the imperial core together, but the Arabs and Turks have taken out the western chunk. Persia is still #1 and has made the game since then a lot of fun, since there were at the Vikings spawn only 5 civs instead of 9.
So, yeah. I screwed up big, but I do think it's doable. I had almost 7% of the land, and had I taken Abdju and razed Sparta, with another city in the Caucasus or India, I could have made the land goal. The Prophets are easier, I just did it wrong. The wonders are quite easy; Parsa and Nineveh have very high production, as does a well-placed city in Anatolia. It can be done on Monarch.. but by a greater leader than I.
Just now I'm playing as a Rome with modded RFCW (REALLY small maintenance costs + 2 stability from courthouses). and I think that cities costs should be lessened (but maybe not as much as I did 
