@boiga:
I think this thread works for it, because we can't really discuss Dragon's motivations without comparing them to the institution he is warring against. From luffy's back story, we know that one of his primary rationales for tearing down the current WG dominated system is because of the corruption of the nobility and their disdain for those with less privilege. The burning of trash mountain was the example of this, but the squatters there were only a small population compared to the bustling city on whose waste they survived. Does the existence of poverty require that those well off need be cast down? Was the problem the system, or the apathy engendered by the system?
And what would replace the current model in Dragon's eyes? Creating a new prosperous social model is much more difficult than casting out the old one (just ask Cuba.) Is Dragon an anarchist? A egalitarian inspired socialist? There are so many unknowns with him. All that has been shown is that he considers the chaos of war as preferable to the status quo. To me, that means the burden of proof is on his shoulders to show that the death and destruction he would cause in his revolution would be justified by a freer, safer, and more prosperous world under his mandate. That's a high bar, and I have my doubts that he could possibly meet them.
I admit that my primary motivation for hoping Dragon is an antagonist and not an ally is because it would allow for some awesomely dramatic fights (sanji vs ivankov!) but right now it seems 50/50 that the while luffy and crew are running the gauntlet towards Raftel, they will be fighting with or through the revolutionaries.
Okay, the bolded: no, I don't think so, and I suspect, though of course I can not know, that Dragon does not really think so either. It seems to me as if what he's primarily against is what you mentioned; the stinking corruption that's highly prevalent in the upper echelons of the system, the nobility of individual nations and the world alike sitting on the type of power displayed in the Sabaody arc. They can point their finger and people die, or are forced into lifelong servitude, or perhaps cast out with the garbage once the noble in question no longer finds them amusing, and no one can as much as lay a hand on them for fear of the immediate and merciless retaliation of the Marines' Greatest Combat Force. This, to me, seems to be what Dragon is against, what he detests and wants to set the people free from. And from what we've been shown thus far, I would argue that the only way to do is quite likely just what he's trying to do; to topple over the entire government. The Marines overall are a good and beneficial entity, but the leaders are rotten. None of them seem to even think of speaking out against the cruelty practied by the Celestial Dragons; they allow slave trade, though they possess the power to end it in mere hours should they want to. In essence, I do not think Dragon wants to cast down all those well off; he wants to cast down those who treat other human beings like less than the dirt they step on; the ones that abuse their virtually limitless influence over their government, inherited through their family lineage, to cast innocent people into a living hell on a daily basis. That, to me, appears to be Dragon's greatest motivation.
Well, to start off with Dragon has shown clear disdain for the fact that war and violence is the only way to truly achieve this goal; he is not happy about it. To me, this indicates that he has not lost sight of his moral compass. He believes that his ideal ends, whatever they may be, justify his means, but he still regrets the fact that these means are necessary. Which, IMO, stands in stark contrast to how government-bound practitioners of "absolute justice" seem to feel regarding their duties. Akainu showed not a moment's hesitation or regret when he murdered hundreds of civilians in cold blood on the off chance that a criminal may be hiding on that ship. The reasoning behind it isn't evil, or even any different from what Dragon is doing - they both follow an "ends justify the means" type of reasoning - but surely you would agree that the attitude displayed by Akainu and Dragon, respectively, toward being forced to resort to violence to achieve a greater end is a clear indication as to which one of them is the "good guy" within the context of the story?
As for what Dragon would set up in place of the current system… it's again speculation, but I get the vibe that he would at the very least want to loosen that iron grip that the WG has held for 800 years and counting. Whether he wants to disband the WG entirely and give nations full sovereignty, I can't say, but some aspects of the system that I expect that he'd be getting rid off are the nobility's influence over it, the relentless hunting of people who fly a Jolly Roger regardless of whether they are actually a threat to people or not and the brutal consequences of refusing to partake in the union (inhabitants from such countries were sent to build that 700-year old bridge, were they not?). Essentially, I think he'd want a lot more freedom at the cost of losing a decent slice of security.