Isn't there some way to get hypertext into man pages? Eg extend nroff. Then you don't have to have a parallel system.

You can use w3mman (it installs with the w3m package on OBSD) and you'll be able to follow manual xrefs. Html output with links can also be generated, see the afterbook man page linked above for an example.

nroff isn't the problem, the pager is. I view manual pages in acme and they become very hypertexty. It's not perfect, as they weren't written with that in mind, but it's damn good.