well, they get the spartan mercenary Xanthippus by script, and the punic war is also scripted, if either SPQR or Quarthadastim is attacking Messina. A complete script for "wars" ( guiding armees of all factions in order to get correct invasions ) is a bit more tricky and imho not worth the effort.
I'm not very familiar with the RTW sripting system, but imho the following would happen:

1. It would make the game linear. Every game would play the exactly same, beacause every AI Faction would act the same.

2. It would make the game much more buggy, because of the heavy scripting work needed, there would be much more sources for bugs to creep into the game,. Only because of the pure mass of scripting text needed to get such a system working. Also it would afaik make ai turns longer again. The old puppet ruler system, which provided level 4 government cities with governouers placed by script, slowed the the AI turns extensively down.

3. It would take a lot of time, and with a lot i mean months/years more of work. First it has to be planned who attacked whom with what general and what army compostion for a time of 242 years, and for all factions. Then everything had to be coded.

If you are complaining that the romans have to much money, then you should definately try to play a different faction. The Romans and the Karthadastim are very easy compared to other factions, because of their wealth and their extensive range of good soldiers. But if you look to other regions of the map you'll find much more challenging factions.

Try playing Aedui, Averni or the sweboz. It will take you years to get out of the red, and even then you are not making much money.
Also the small Asian Kingdoms like Hayasdan or Pontus are a good choice for gettig more diffcult games, because of their geographical near to the military powerhouse Arche Seleucia. Hayasdan is also having an interesting game mechanic about restoring the persian empire, which affects both the military units and the building choices.

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