Let's say there is a problem reported in the field which requires a hotfix. Well, if you are doing traditional software development, you can't exactly ask the customer to wait until you finish your current release. And if you were to put out a fix for them using your main development process, that would probably take too long too. So, you have a hotfix development process. By definition, this is a development process which is not used for regular development and it is not used very often (so one would hope).
As a result, you have one process for regular development and one process for hotfixes because your regular development process takes just too darn long. That means that when you most need for things to go smoothly you are going to use the process which is the least practiced and probably also something that only a handful of folks know how to do or are allowed to do. What's wrong with this picture?
The solution is to get the path from deciding to make a change and being able to deliver that same change as short as reasonably possible. If the "overhead" from start to finish for a hotfix is 4 hours, then any development task should take you no more than the overhead plus however long it takes you to write the code and the associated tests. All development tasks should follow this same streamlined process, not by cutting out truly necessary steps, but by ruthlessly removing steps that add no real value and automating as many of the remaining steps as possible.
Once you have a sufficiently small overhead, then you really only need one development process which you use for both regular development and hotfixes! Since it is the same process, everybody is practiced in your hotfix process and everybody has experience with doing it. This will reduce risk and increase confidence in the results.
In practice, there will probably be at least two differences. It is unlikely that anyone needing a hotfix will want to take the risk associated with taking any changes other than the hotfix, no matter how ready for release you say those other changes are. So, you will need to develop the fix against the release that the customer is using. You will probably also deliver the fix using a slightly different path than the usual. However, the closer you get to just these two differences, the better off you will be.
There is a shortcut you can take on the way to getting to a single process. You can refactor your regular process such that you act like every development task is a hotfix, and then do the rest of the process in a second stage. For instance, if you normally do a subset of your full test cycle for hotfixes, then always do that subset first during regular development.
For some software projects, getting the full test cycle down to a short time frame will be impossible or impractical. In this case, refactoring to have the first stage be the same as the hotfix process is still recommended and keeps you focused on keeping the second stage as small as possible.