I humbly propose:
USB 4.0Gen 0a (USB 1.0 speeds)
USB 4.0Gen 0b (USB 2.0 speeds)
USB 4.0Gen 1 (also USB 2.0 speeds)
USB 4.0Gen 1z (USB 1.0 speeds again)
USB 4.0 (20 Gbps)
USB 4.0e (40 Gbps)
USB 4.0Gen 2a (also 40Gbps)
USB 4.0Gen 2e (80 Gbps)
USB 4.0Gen 2f (charging only)