I just don't really follow your logic with the first part, nothing is fundamentally changing.
The system is changing from an altruistic one to a presumed consent one, and that is a fundamental change.
The problem I see with this kind of presumption is that silence is presumed to mean consent and that is a dangerous presumption to make...there may be a myriad of reasons why an individual has not opted out, including a lack of understanding of the process, not having the mental acuity to make such a decision in an informed way, not having access to the process for some reason or not being aware of the process and I am sure that you are able to discern the rest and possibly more.
I feel that better ways could possibly be found that do not make a presumption, such as Family Consent being found at such a time as necessary (as in the US) or a system whereby consent is sought at predetermined stages in a persons life, such as their Age of Majority....I have no specific opposition to a compulsory system which asks for a choice at a predetermined time as long as their is no discrimination or prejudice attached to whatever choice is made and that the individual has the choice to abstain if they wish and can retract whatever choice they made at a later date if they so wish. We could potentially add it to the Census for example.
I am opposed only to the concept of presumed consent, not the concept of Organ Donor-ship which I support.
Currently the government decided for you that you don't want to donate. How is that any fairer, especially for those dieing while waiting for a transplant because the government has decided the default position for everyone?
The Govt have not decided anything for you, it has made no choice it has simply not exercised any definitive position on your behalf, as it is a null position, no consent or objection is registered so no action is taken.
As to the latter I agree, people should choose to donate or not and the outcome should be no different. However, it is not at all like choose not to help with defence. People basically have a choice, do you want to receive an organ transplant in the case of an emergency or not? If not then you are free o do as you wish, if you do want to receive an organ in an emergency then what right do you have to dictate that you can use other people's organs but none can you yours? It is a very strange and fundamentally selfish position to hold. But I wouldn't agree to such an arrangement because people shouldn't be punished like that.
I think it is similar to a conscientious objection, as the objection is one of conscience. You could argue the same selfishness is inherent in such a position. I wouldn't agree as I feel that an individual should not be prejudiced against because of a statement of conscience.
I feel that in all cases where a specific statement of consent or objection has not been made, the decision should be one made by the family and not the State, and in the (I would suspect quite rare) situations where no consent can not be sought then the position should be one of
Do Nothing.
Also, don't mistake all the things the government already force upon you. You have no right to change the taxes you pay just because you disagree with the way the government spends it s money. You have no rights to change the law because you disagree with them.
I am aware that there is some things in society that I cannot change as an individual alone, although I can potentially change anything if I have enough support or if I wish to object and pay the consequences under the law as it stands. I do not see the comparison between paying Taxes as set by an elected Govt and the default position of the State over the disposition of my Body if and when I die and have not made a specified choice. Consent (where appropriate) should always be a sought position, not a presumed one. I feel that is a fundamental right that every individual should have.