Well imagine my surprise. (i)

I have a horrible feeling that if you found all my posts where I'd gone off on one about the awfulness of computers, you'd also find companion pieces that mostly read 'S'alright. Fixed it.' that arrived a couple of days later.

Is that good? It's probably good.

Solutions:
i) Use ISC Kea for DHCP(4|6) server(s).
ii) Use dhcpcd5 for the client.
iii) Write a sed(1) one-liner that runs as the last thing in yr preseed script and comments out any 'iface eth' lines in /etc/network/interfaces.

Well, I say 'write'. I mean 'find on the internet like everyone else.'