You can already throw out any diplomat you want without giving a reason under Vienna-style conventions; You just declare them persona non grata, send a letter and voila. Furthermore:
This is a popular myth, however embassy grounds are not considered parts of the territorry of the sending nation under international law. For example, the buildings have to abide by local building and fire codes, and you don't have to present a passport of subject to customs inspections when entering.2. Embassy grounds are treated as though they are part of the territory of the embassy nation, but violating whatever airspace or underspace they may have is not considered to be illegal or an act of war in any sense.