I just stopped myself from legacy IP thinking.
I'm planning a new Wireguard link between a pair of servers and was about to use a small IPv6 subnet when I caught myself.
Thanks to our amazing home ISP, not only do we have fixed IPv6 and legacy IP addresses, but we have a massive /48 of IPv6 space available so for a home network, plus guest and iot WiFi, and a few lab vlans, we really do have a practically unlimited amount of address space available (65535 /64's, each with 18 quintillion addresses).
So, even though it's a point to point link, I can just allocate a /64 and pick a pair of addresses from that range. This isn't legacy IP anymore, stop thinking that way.
I could of course just use a pair of link local addresses and the traffic would (should...) still flow but if I use GUA's from my allocation instead, I'll get proper responses in traceroute if I need to troubleshoot.