[labawi]

What does the wifi handoff you mention actually do?

I know of a standard for 802.1X preauthentication, that does 802.1X authentication via old AP before roaming.

If your APs aren't doing NAT or stateful firewall, then there is no state to transfer, except automatic updating of MAC addresses on switches, and the authentication of the client which shouldn't require any cross-communication unless using 802.1X with mentioned preauthentication. You will lose packets in flight while switching, but it shouldn't take long.