I've managed to get something to run, but unfortunately can't share it due to company policy. Nevertheless, I'd like to share it in case somebody needs it.
The approach is not superfast, but I think it is not permissively slow when run regularly and the wiki is not too large.
I've implemented it in R using shell tools (that also come with the Rtools for windows), so it doesn't fit perfectly in the dokuwiki universe.
It goes like this:
-find all new pages np and extract their first header nh as well
-for each np:
-grep all other pages for page name and nh
-for each grepped old page op:
-cut the text of op into a single-word list
-from start to end of the word list:
-keep track of environments (lie '[[.+?]]', '{{.+?}}', '<[a-z]', '</')
-outside environments, look for name of np and nh and replace with a link
-stop after first occurence found
-if something changed, use dwpage.php to checkout op, insert changed text, and commit op again.
This of course does not look efficient at all and it isn't. In practice, the time strongly depends on the number of new pages and the corresponding pages grepped.
Running it on a weekends night for a company wiki should work fine, especially if one is runnning a group of maintenance scripts (cleaning up the attic, rebuilding the searchindex) anyways.
Finding all new pages is simple on R/windows - just use ctime from file.info(). It also seems to stay unchanged when modifying a wikipage (Yeah, this is the first time windows is useful to me). Finding all new pages on R/unixish is probably a bit more troublesome (but check
http://stackoverflow.com/questions/23318695/how-to-get-true-file-creation-date-in-r-on-unix-systems). Since you would expect the number of new pages to be much smaller than the number of new+edited pages, it would be a rather good idea to be picky here.
It would be a smart idea to check the list of new pages and headers against a page called something like 'the'. Maybe a length check or combined with a dictionary that contains word-probabilities in the respective language. Otherwise one could severely fuck up ones own wiki.