Multiple ScriptedImporter for the same file type

Is there a strong reason this is explicitly disallowed? I wanted to write a custom importer for Tiled (the editor) maps (.tmx) in order to automate some processes we would otherwise have to do manually, but I'm already using another library that does stuff with .tmx files using a ScriptedImporter and therefor it doesn't work.

 

I just noticed that there is AssetPostProcessor... can we use that in conjunction with ScriptedImporters? Would actually be the perfect use case for me.