All these support issues could be avoided by separating proprietary code into a precompiled static lib that the plugins could be linked to. That way source files can be included that have no problematic code and can still be recompiled for source projects and custom engine builds. I can’t tell you how many times I’ve had to make plugins work ahead of official releases cycles or upgrade code to match minor engine changes. In my experience unless a plugin is recompilable it becomes a massive thorn and an impediment to content production.