"What's interesting is that civilization simulators (like Civilization, Europa Universalis, etc) don't take this into account."
That's an AI problem moreso than an economic problem. Modern warfare has elements of both chess and poker (and others of course, but roll with me here). The chess elements come from accumulating threats and counterthreats and so on which are all important, even if they never manifest. For a clear real-world example, look at the North Korea standoff, which has frozen the same basic threat/counter-threat model in place for decades; North Korea can not win a war, but they can cause more damage then its worth before we can destroy their ability to damage South Korea. It's a very "chess" situation, only there's no clear endgame. The problem is that in the context of those games, the computer players aren't smart enough to engage at that level of strategy; at most, if you build up a large force you'll make them "nervous" and they unconditionally attack, and that only for game balance reasons, not realism. The computer players are not able to take in a complicated situation and understand it deeply enough to participate in truly modern power struggles.
Your last suggestion is game unbalancing; in that case, everyone will simply be in a perpetual state of open total warfare, from the instant you start that bonus. That might be a viable game but it certainly would be a different game.