Here is a beginning of a rcs plugin that uses rcsmerge, rcs, ci, co and rlog. I have used it probably over hundred times but needs some work.
http://www.reedmedia.net/~reed/tmp-sfhkcjkfrfh/rcs.pm
Clearly needs some cleanup and perhaps some of the missing stubs implemented, before it can be included into ikiwiki.
Notes on individual functions:
rcs_prepedit - I'm not sure why you do the locking since the comment notes that the locking does no good..
rcs_getctime - You ask why this would be better than mtime. It's because with something like subversion, a file's modification time or ctime is not necessarily accurate WRT when the file was first checked into the repo.
--Joey
Also here is a quick script to browse the RCS history to use for "historyurl".
http://www.reedmedia.net/~reed/tmp-sfhkcjkfrfh/rcshistory.txt