The "Internet Mobile Host Protocol" (IMHP) was written as a draft RFC in 1994. As far as I know it was never adopted, but is it still relevant, even as an inspiration for IPv6?

[1] https://www.cs.rice.edu/~dbj/pubs/draft-johnson-imhp-00.txt

Edit: Its official entry at the IETF: https://datatracker.ietf.org/doc/draft-johnson-imhp/