One of the advantages cited for SRv6 over MPLS is that the packet contains
a record of where it has been.
Not really ... packets are not tourists in a bus. First there are real studies proving that most large production networks for the goal of good TE only need to place 1, 2 or 3 hops to traverse through. Rest is the shortest path between those hops. Then even if you place those node SIDs you have no control which interfaces are chosen as outbound. There is often more then one IGP ECMP path in between. You would need to insert adj. SIDs which does require pretty fine level of controller's capabilities to start with. I just hope that no one sane proposes that now all packets should get encapsulated in a new IPv6 header while entering a transit ISP network and carry long list of hop by hop adjacencies it is to travel by. Besides even if it would it would be valid only within given ASN and had no visibility outside. Thx, R.