The moral bit is choosing between 2 competing blood donations service - one that is run publicly to save life, the other to extend the life of healthy individual. I make the assumption that the remuneration of the second one will be most likely way bigger than in the first case. The only reason people would chose to donate to the first one is morality which is unfair.

The morality of the remuneration is orthogonal. I assumed we were talking about countries where it is moral and legal to remunerate blood donation. I don't think that countries that today do not allow remuneration (for any reason) would allow it for this new use case.

You can still use blood from a private company for the treatments you would use "public" blood for.