Note that it's being updated to use XML, that change should be available for use in the next couple of weeks. I'll need to make sure to document this stuff on the wiki so it's clear how it works.
It'll look something like this (i don't have the code handy atm):
<xml version="1.0" standalone="no"/>Not that different, but it'll eliminate any issues with long names, since the original parsing code uses fixed size buffers.
<replacement_map>
<keyvalue key="models/scientist.mdl" value="models/female_scientist.mdl"/>
</replacement_map>
Per-entity replacements aren't supported yet but that'll be added eventually, the essentials are already there.