Hello Andrea,
Yes, it is possible.
However, the original idea of this feature was to allow for a workaround to the projects that require to modify the part of the tiled models. For example, build a solid block mesh for some region of the large project, if necessary - edit it and re-import, and then run the mesh based tiled model generation with "merge tiled model" option enabled, in order to merge it back to the original tiled model following the same hierarchical model grid.
The tiled model merging process is not that straightforward, as the tiles do not correspond to each other for different projects. We'll be working on the solution, but the mentioned feature hopefully should be helpful at least in certain cases.