One potential strategy is to take advantage of your allies attacks.
Basic Strategy: Shift a general and a couple units down to your allies fronts. When they besiege a city, seige alongside them. Build one siege weapon. The very next turn, attack. If neccessary, open the gates. Then, sit back and watch your allies die painfully trying to take the city for you. Oh, and because you initiated the attacks, guess who gets the city. That's right. YOU!! (Fond memories of taking 3 casualties, and watching 100's of little red bodies dotting the ground, after they took the city for me) Even if your allies are slaughtered, if they've done enough damage, you can take the city with a token force. (more fond memories of taking Syracuse with a general and a hastati, then rushing to Massaila). Leave small little armies near your allies borders to watch for movement.
Once as the Brutii, I took Patavium, Mediolanium, Syracuse. and Libybaem, then expanded to Massaila, and Luvavum, and held the fords against the barbarians. Watch out though, as the Brits will recreate Charlemagne's empire + Spain and Dacia. This is quite heard to defeat. Try pushing into Germany and holding them at Mediolanium and Damme to prevent them from spreading east. Effectively, hold the rivers, and the larger cities, against them. In the South, take Carthage, Thaspus, Caralis, and give the Scipii Lepcis Magna as a buffer state. Take Greece, and then do what's normal. Be careful though, as because of all the extra territories, the Civil War comes early, like right as you meet Egypt, and you'd be amazed at how many armies 6 cities can pump out. Have a least 1 matching army on every front. Try removing trade rights to limit their economies. If you want more details, just ask.
[This message has been edited by Meyerk (edited 02-06-2009 @ 08:41 PM).]