With A1, A2 and A3 being with just one person, that is he will have to back 3 keys and 3 Seeds.
All 3 keys can be derived from the same seed.
Then if this seed gets compromised, wouldn’t the hacker use them to recover all the three keys? Although the hacker would still need one more co-signer but wouldn’t that be too risky and probably defeats the whole idea of multi sig?