If your concern is that it will reduce the supply of blood to younger people who currently use it then this is something that can be solved with incentives in a way that everyone benefits (e.g. people using it for rejuvenation pay more to subsidise higher production and are a lower priority when there is insufficient supply in the emergency room etc).
If on the other hand, that is just an excuse because you're morally opposed to old rich people living longer... ?
I don't really see how you provide incentives that go the way of blood to the hospital without paying donors that explicitly donate towards that goal more than those donating for rejuvenation.
Right now, we don't have enough just for the people in the ER. Not saying it can't work, but it seems to me that the potential for catastrophic failure on a social level is quite high.
If on the other hand, that is just an excuse because you're morally opposed to old rich people living longer... ?