Its somewhat possible to get a spawner block with the entity data inside of it using scripts.
The publicly available addons that do this (linked in the comments below) are completely obfuscated. While its possible to deobfuscate them to a degree, finding the specific process or function to do this would take forever and might break the license agreements within those addons.
Any information will help a lot, and will lead to an open source addon, with everyone involved credited.