That's unfortunate. I'm not really an expert on online mods, but there's probably more rules regarding stuff like hitboxes and animation playback speed than with sp mods. This probably means recompiling the models at the very least.
This is usually a point where a lot of people who are used to "what you see is what you get" game engines get frustrated, but compiling a model isn't especially difficult, it's just time consuming. There's lots of old tutorials floating around.