IPv6 equivalent to intercept outbound traffic from host?

[te]

I'm trying to figure out the best IPv6 equivalent to redirect outbound traffic from a specific host to another to actively intercept the network traffic coming from the host. I do a lot of device testing which are often embedded or similar devices which I do not have direct control over. I want to trivially capture the traffic leaving the device.

In the IPv4 world this is easiest to trivially accomplish with a simple NAT rule:

Interface: LAN
Protocol: TCP
Source: Host.IP.0.10
Destination: !LAN net
Destination Port: 80 (or whatever)
Redirect Target IP: MITM.IP.0.5
Redirect Port: 8080 (or whatever)

And all outbound traffic to port 80 is redirected to the local MITM host. There are other methods, sure, you could probably make a static DHCP entry where you set the default gateway for that client and accomplish something similar.

For IPv6, without NAT66 support that method doesn't work though. In practice, most of the time, testing can be accomplished by simply disabling IPv6 for the device VLAN to force the device to just use IPv4, but this isn't always guaranteed to work especially as some IPv6 only devices and servers are showing up. In cases where the physical device is right in front of me I can isolate it by using a laptop running Ubuntu or similar with two NICs and doing NAT on that where I can use iptables and NAT66 to redirect the connection locally, but this isn't always easy or practical, especially if it only connects over wifi or if the device is just on the same VLAN, but not physically on my desk. It works, but I end up with 5 PCs, a bunch of a devices, and a pile of cables on my desk. The NAT solution is easy, it's a few clicks and the packets show up where I want them to, on a VM, at my desktop, wherever.

What's my best option using pfsense to do something similar with IPv6?

I'm just racking my head how doing something simple with routing or RA advertisements to target a specific device would work. I guess if you isolated the device to it's own VLAN tagging it at the switch level you could do a routing solution by setting the IPv6 upstream gateway in pfsense? In cases where the device doesn't use it's own hardcoded DNS server, you could possibly give it a local DNS server through RA that returns the MITM.IP for all requests from a specific host? Not infeasible, but definitely more work.

Am I missing something obvious, how would you do this?