...if you are able to choose whether to introduce a new language for some components... Well, there are complexity, readability and maintenance costs associated with introducing any new dependencies into a project. And (in my opinion) these costs go in the following order, from small to high:

1. header-only library 2. compiled library 3. compiled library with type framework 4. framework 5. meta-programming framework 6. custom meta-programming framework 7. domain specific language 8. custom domain specific language 9. generic programming language 10. custom generic programming language

As a side note, increase in complexity also might increase job security of a developer. If you are after it, design your own programming language and try to deliver every project implemented in it :) Should your projects be in high demand, your skills will be in high demand as well!

Yeah, there's obviously a cost involved. It's not something I'd want to do more than once within a project.