For a long time it annoyed me that certain Jack applications in Linux did not have a plugin version, so it could not be used inside a DAW without manual port routing and launch scripts, etc. Yoshimi is one example, and there are many commercial examples. While it would be possible to add plugin support for the open source variants, this is not possible for the commercial ones.
I wanted a more general solution, so for a while I’ve been working on a project to be able to use any Jack client as a plugin. The result is Jack2DSSI, which is a DSSI plugin that can host Jack applications inside it. So for example, if you want to use Yoshimi in your DAW project, but you don’t want to launch it manually every time you open the project, use the Jack2DSSI plugin instead. It will save together with your project1, and the plugin makes sure the Jack client is relaunched later.
Check it out on the project homepage.
1 Not everything is saved. See the Caveats section on the project page.