It is hard to get the AI to do what you want them to do. When I 'herd' the AI, I'll usually stick to preventing the AI from taking certain cities, returning lost cities (through diplomacy), and weakening the strong (through cheats: character_reset & auto_win attacker with an army of mercs) so that the weak might rise up.

You can also conquer a city and give it to the AI with diplomacy, but the problem of correct government causes problems (since aquiring a territory through diplomacy doesn't handle governmetns). In these cases, I'll either repair the previous faction's government or build one of my faction (through cheats) based on whichever one fits best. For instance, you are Rome, you take Korinthos from Makedonia and want to give it to KH, since it has a Mak TypeIII, I'll tear it down and build a Roman TypeII, then give it to the AI, which will now have a government # better suited to the town for the recieving faction.