Do you know whether unreal’s GetDllHandle uses the RTLD_GLOBAL flag, or whether it can be forced to use it? Because if VTK is built with shared libraries and if dlopen() is called with RTLD_GLOBAL, then it should work (in theory, at least).
You are correct about the VTK array redesign, the new design uses typeid() in many places. Therefore if RTTI is not working, then VTK arrays will not work.