Well of course that makes it somewhat more complicated.
There are several MODS available that do "something" like that, with the exception of your multiple keywords in one field.
I looked at the standard db.cgi and I find that it setup to handle multiple keyword in a field within sub split_decode. The split_decode is used in the build_select_list subs. I know you are not building a select list, but the code could be modified to build your index.
The first MOD that comes to mind (not sure the format fits your desires) is the spreadsheet MOD, as it sorts, displays multiple fields, and creates links. So maybe after a running the record through the split_decode sub you could use the spreadsheet MOD?
I too would like to be able to build a "traditional" index from dbman using multiple keywords in a single field, ( I have been working on it on and off for some time ) it will be used for an annual research report. I currently build a static index from a database using many-many steps, the final format I desire can be seen at the link below. This is what I am calling "traditional", let me know if this is the layout you want or something else.
http://mccoy.lib.siu.edu/...dex-weed-common.html