Premise one is unsatisfactory. If you do believe that the first premise is correct then you must believe that an innocent game of Russian roulette is morally permissible as long as two consenting, competent adults were involved, and it did not violate any other people's rights. Russian roulette is however considered wrong because it is against one's own interest. Because of this argument also seems to need more to become a successful argument. The last two arguments are both weak alone but if we can combine these two arguments into one I believe that we will then have a strong argument.
Active euthanasia is morally permissible.
This argument uses both the Mercy argument and Autonomy argument in its attempt to make a very strong and convincing argument. I believe that it has succeeded. This argument, if you wish to break it down, says that if someone is suffering with a terrible illness and death is in the person's best interest, then as long as the assisted suicide does not violate anyone else's rights and the act is done by consenting, competent adults then it should be deemed morally acceptable. Whether or not voluntary, active euthanasia should be performed is a tough question to answer because of all the problems that you are likely to encounter on both sides. You may believe that one should have the right to choose to end their life for their best interest, or not.