How realisitic in large companies?
What you describe indicates a weak planning. Needs to be a project Manager who organizes the planning process will involve Prodakt Ovner, Teamleads group and himself. The result of planning should be the Gantt chart or Roadmap which would take into account relationship will be established and adequate risks. I always do, and my projects almost never is such the blockers as you describe.
About realisitic, there are different methods.
Versioning is good if you are working through the API, but if you have several teams of backend are sawing the same monolith it is necessary to introduce the practice GitFlow and put tahlia to deal with mariami branches in the releases and correctly build adequate GitFlow.
Versioning of API is a great practice, she needs to learn not to listen to those who say that it is difficult. It is not difficult. And the versioning will allow to release the backend without waiting for the frontend and not breaking it in production.
What would the releases went smoothly you need to immerse yourself in books on Continues Delivery and activities dobereshsya their services or monolith.