[The problem with the current tax system.]

"Still, 1 major feudal system remained in place, the taxes." This statement is false. The concept of feudalism as proto-capitalistic is an invention of Marx; and a particular failing of Marx's adaptation of the Hegalian Dialectic, and socialist thought, like yours that relies on it. Rather, taxes pre-date feudalism by approximately 3000 years. (http://www.upenn.edu/almanac/v48/n28/AncientTaxes.html) They are not an instrument of a repressive form of government, rather they are the instrument that defines a government. You cannot have a government without taxes.

[To follow or not to follow.]

If you're going to lose, you don't have to follow.

I don't think this is the standard the majority of people actually use, with a few well berated exceptions. Rather, I think its: "If you are going to lose, and you think your ally (or their ally/ally's ally, ect.) behaved like an total idiot and probably deserved it, you don't have to follow the treaty."

[To follow or not to follow.]

From a purely functionalist standpoint, there is no way to 'enforce' a treaty as binding to all parties. Hence, the social mores against not following a treaty functions as its attempted enforcement. Alliances, assuming perfect knowledge, will act in what is best for their own best interests, treaty be damned. If an alliance follows a treaty, its only beacause they feel its the best course of action. At the point in time a treaty is activated, each party decideds first if it is in their best interests, then constructs a nominally fact based argument to back it up. Lesson is, don't treaty with an alliance you doubt will share your interests, and re-evaluate often.