What type of data is inside your 3D Tiles? There may be a few workarounds you could do in the meantime (one idea is using clipping planes to cut out pieces of the old tileset to place the new one).
The main benefit of 3D Tiles is to make it possible to share/visualize/analyze datasets that are too large to work with as one chunk. If your data is small enough and you just need one model, you could export it as one model from PhotoScan (in a format such as glTF, or convert it to glTF by uploading it to Cesium ion).