I like it as an idea. We'll see if it gets any traction outside of Scala-land.
There are some methods in BSP that might merit inclusion in LSP like buildTarget/test and buildTarget/run.
However, there are some critical methods in BSP that make no sense in LSP like buildTarget/scalacOptions. This is a method to extract dependencies and other compiler flags that are necessary for a Scala language server to provide completions, navigation, etc. Currently, every Scala IDE builds its own "export" command for each supported build tool resulting in duplicated effort. With BSP, we hope that a build tool can implement the server once and in return get integrations for multiple IDEs.