I see where you are going. But the recipient doesn’t need to be the donor. You don’t need long term storage for use in an unrelated patient in a matter of days or weeks.
Try reading up on the match rates.
Yes, cord blood allows a 6/8 match on immune system markers to proceed; but you still have to do a preliminary typing, and a lot of those don’t pan out.
Matching to minorities such as African Americans is particularly hard to accomplish.
My last remark is within the context of leukemia / etc. where you take out the patient’s immune system.
Haven’t studied it for infusion of stem cells in other cases; but the issue there is the small amount of stem cells within each umbilical cord.