I'm not sure you can preserve
O Sensei's Aikido. He didn't try to do that, since you can see it change by viewing films made over his lifetime.
While you can restrict yourself to train in the physical forms that O Sensei used, it will never be
the same. As your understanding of the art grows, your performance in it will differ, even if you use the same movements.
Aikido is not a Platonic Form
that is preserved throughout eternity. It is about the moment and the changes within that moment.