Since fields like this have so much speculation and so little hard data to go off of, they have to resort to historical analogies for much of their analysis. Who really knows if China's South Sea strategy is the result of a concerted turn towards militarism, inflamed nationalistic sentiments forcing the government in a particular direction, a geopolitical priority based on projected energy needs, emergent behavior from different factions struggling for power, or a combination of these things? Especially when it comes to a political system and government as opaque to outsiders as that of China? And so we reach for the tired, ill-fitting Bismarck analogies and maybe dredge up some three thousand year old historical event that we imagine might provide some sort of insight.
Also, the guns to butter argument doesn't really make sense. You can't just spend lots of money to quickly buy up a fully-trained military. It takes years, even decades of operational experience to develop a competent fighting force, experience that simply cannot be purchased.
I believe the key is to be a bit more loose with the "guns to butter" analogy. The strategy isn't really to "buy up a fully-trained military" but rather to direct a large proportion of the GDP to building one at whatever time-scale is required.
If you were to do this as an up-and-coming nation (i.e., you've got just a little butter), you'll meet strong resistance from your peers: they know they can counter you by putting your butter pile at risk.
But if you first pursue a strategy that gives you a mountain of butter reserves, your peers lose much of the leverage they can exact upon you, and you are free to devote massive resources toward military with minimal "worst-case" economic risk.
EDIT: I made another comment about how interesting it is to relate this stuff to strategy board games, and this is an example that converts pretty well: "don't start bludgeoning your neighbors into submission until you're pretty sure that you no longer depend upon them for basic resources." is the strategy. (The alternative strategy would be to constantly be frienemies: take a little, give a little, injure a little the whole game, rather than to have a phase of friendship followed by a phase of foeship).
Also, the guns to butter argument doesn't really make sense. You can't just spend lots of money to quickly buy up a fully-trained military. It takes years, even decades of operational experience to develop a competent fighting force, experience that simply cannot be purchased.