I used this strategy quite successfully in a recent PBEM game of 200BC: My only hero was killed and I had little money nor any good prospects of geting much. I had also lost my banner, so when I got a new hero, I hired and immediately disbanded! This gave me new allies for (almost) free every several turns. In a scenario with lots of unexplored ruins, the promise of capturing good items, or cities building allies, this may not be good strategy, but it worked great for me. I hid all the allies under other pieces and when I was ready for my big move, produced some major surprises for my opponents.