I love how everybody assumes a person is guilty before said person has been tried, and actually found to be guilty of their accused crimes.
I'm not saying he's a saint, but the whole fabric of the US legal system is you ARE presumed innocent until proven GUILTY in a court of law. The fact he was a playboy style multi-millionaire and had fortunes most of us could only dream of is absolutely immaterial -- he is entitled to exactly the same rights as the next person, and in the eyes of the court, and the legal system should be treated the same.
His allowance is a lot of money but it is proportionate to his living expenses for the lifestyle he led, and for the ongoing costs (which includes his family home) he occurs. Added to which, the amount he was given by the NZ courts was specifically (and only) for living expenses. Therefore the US government cannot "force" him to use that allowance to pay for legal representation and Dotcom has every right to apply for additional funding from his seized assets to cover the costs of it.
And that doesn't even bring into consideration the fact that Dotcom's company, Megaupload requires representation in court, and currently has absolutely no money in order to pay for such services. The financial circumstances of Megaupload and that of Kim Dotcom are two separate issues. Megaupload needs to pay for legal representation from its own company funds, which have been seized and therefore this is impossible.
At the end of the day, his income, however sickening you may feel it is, is exactly that until he is tried, and found guilty. You can't refuse his finances for legitimate reasons when you don't even have a conviction to suggest they're any different. He might be found guilty of his crimes, and the money might not be his legally, but until that conviction is given, it cannot be treated as such.
The latest lawyer firm that wishes to represent him should be allowed to do so. At the end of the day Dotcom is protected by the conflict of interest rules, and his decision to waiver them, as well as the law firm being happy to represent him should be taken into account. If Dotcom is aware of the implications of having them represent him, and accepts them, the government really shouldn't be dictating otherwise.
To suggest that he cannot hire anyone who has any previous experience dealing with conflicting clients that Megaupload's servers might contain the works of is outrageous. This is not the case for your small street corner law firm, and will require the services of specialised and highly experienced copyright lawyers with considerable staffing for the investigative and legal work a trial of this size requires. The US government even suggesting otherwise is without question turning this into a complete "show" trial and denying the accused of the legal team required to adequately defend himself in court.
Finally, the NZ legal system ought to be watching this closely. As it stands right now, Megaupload and Kim Dotcom are not being given "fair" opportunities for legal representation, and his extradition should only be granted on the condition he is. Extradition laws are supposed to ensure a person being extradited isn't consequently unfairly treated -- in that respect, the US government are almost feeding him ammunition to aid his defence that he is being poorly treated.