but how can I specify the Substitute pattern(s) for this particular
provider while leaving this in for another substitution provider?
I think this is a dead end, the mod_substitute filter will see all of
the Substitute directives. Maybe this is possible in 2.3 with If?
Basically I have a working configuration of mod_substitute and
mod_filter that always attempts substitution in text/* content. It's
configured roughly like this:
LoadModule substitute_module modules/mod_substitute.so
LoadModule filter_module modules/mod_filter.so
FilterProvider gzinflate INFLATE