DynRes - if memory serves lets you specify which files to load from disk and which to load from module/hak.
Both plugins will prioritize what is in the externalsources directory - over any embedded files.
I think this may also override haks - but don't quote me on that.
Types of files that can be overriden include:
nss / ncs
character files / creature files
items
areas (gic, are)
blueprints of any type
journal (jrl)
factions .fac
Some of those however, only get loaded at startup - so for them to take effect (particularly the journal and factions), you may need to reboot the server.