When you need a special feature in a FOSS (Free/Open Source Software), you simply go ahead, make the change and submit your changes as a "patch". If your change is meaningful and should become part of the FOSS, it would most likely be accepted. Otherwise, you have the change in your local tree. The important thing is that you get the feature you wanted.
In a proprietary development environment, you do not have this luxury even if you are part of the same company that has developed the software that you want changed. This is how I have seen it working: you make a request to the team responsible for the software. If you are lucky, they will agree with your requirement and add it to their roadmap. Depending on many factors, you may get the feature implemented within few months to few years. But this is no good, for your deadline was much earlier!