What do you mean by tempremental? His mod has a temperment?
The reason it won't "except" mods is because it installs to your Generals/ZH game dir instead of the Data dir (where mods should install). He probably did this because not all files can be read from a big file, but a simply launcher could fix that as seen in Second Wave and Blitzkreig 2. The files in Pro:Gen overwrite any mods you may try to use with the -mod command line. The only way to play other mods is to un-install it. That's the only reason I don't play Pro:Gen
Too annoying to have to constantly re-install if your a modder or a frequent mod user.