Originally Posted by
Ovidius Empiricus
It was a choice, in the sense that nothing physically or logically forced them to make that choice. Of course, Akragas doesn't need to become a Huge City, so it's already a matter of player choice.
It was however a smart choice to make (at least it seems so to me in hindsight), due to external circumstances like economic considerations and changes in the way their enemies fought. So if we were going to simplify that enough to model it in the game, some economic factors and/or changes in an AI faction's construction/recruitment or economic/political systems would ultimately be the reason for the Roman reforms, which is not to say those come in the form of an immediate cause of them (as a mechanic in the game triggering it without your choice would simulate). What this suggests is that the Romans need to face an increased challenge from AI factions in the form of their better economies and better militaries, so that Romans "must" get to the reforms in order to compete in this sort of arms race. In other words, the other factions ought to have "reforms" of some sort too -- at least some of the major factions, but not "free people" or perhaps others.
At present, it seems to me the situation is already very easy for the Romans. (That's not necessarily true at the very beginning of the campaign, but once it stabilizes, you can effectively stomp all over other factions with pre-Marian units and conquer the whole map. The rebellions also make things difficult, but this is beside the point and much of it is in any case due to fighting other Roman-style units.) The post-Marian units only make it that much easier, rather than being just enough to gain the upper hand again. Granted, the Romans were historically very successful, for a variety of reasons, and there weren't such vast changes in the way warfare was conducted that the AI needs to start producing impossibly-powerful units or absolutely rolling in cash. But they ought to be strong enough and develop over the long term in some way (aside from having very-costly "elites" available in high-end barracks from the very beginning), so that the Roman reforms seem to be a necessary choice for the player to keep up, even if the reforms are costly in other ways. I'm not sure what exactly can be done, considering the limits on the unit roster have already been reached, but perhaps the AI (and only the AI) should get greater bonuses to weapons/armor/experience/morale from very high-end barracks/temples/foundaries/whatever so that no matter which units they end up recruiting they'll pose a somewhat bigger challenge. And they could have more effective generals: better traits, ancillaries, higher command, etc., in fighting (who will promptly charge straight into a mass of spearmen) and better governors who can reduce recruitment costs and such. I guess these changes could be triggered with the Marian Reforms, so that effectively you've made your own problem to solve, or there could be other things independently for each faction that come into play.