

That’s basically what shortwave pirates are. Usually former ham transceivers modified to transmit out of band. The cost of licensing and building a shortwave broadcast station are immense. And there’s the pesky problem of finding advertisers when the license scheme basically requires you to at least look like you are targeting non-domestic audiences. Hams have occasionally purchased time on existing transmitters when it’s cheap, but as far as “experimental modes” go, it would typically have to be something that can be modulated by an AM transmitter.
I agree, a low power SWL license scheme would be fantastic. If you think you can convince your representative to advocate for it, go for it. Currently, even low power community FM is barely tolerated as a license class, and regulators tend to think of SWL as REQUIRING that the targeted audience be non-domestic.