My understanding is that there is a way to implement IBC on chains that are not Cosmos, without needing to adopt the Cosmos SDK.

That might be true, I only gave it a brief look, and you certainly have read more about Cosmos than I have.

It has the potential to bring interoperability to a whole new level, that's certain.

I don't know if it could be used for layer 2 solutions - beyond my simple mind to figure that out.

I see @dragosroua who commented and who knows quite a lot about Cosmos and Hive from the technical point of view also believes a second layer implementation would be a better solution for Hive.