That depends on what the tweeter faceplate is designed to do. If it's simply protection from fingers, changing it won't be a problem. If the faceplate includes a small disc placed very close to the center of the dome--the disc may have a small hole in the center, then changing it may be a big problem. If it's the little disc, it's designed to reflect some of the sound back to the dome which will boost some frequencies and attenuate others. The frequencies affected depend on the size of the disc and its diameter. If it's one of those, you'd have to replicate it precisely to have the same frequency response.