What you're describing doesn't make very much sense. There are only two cases here:
1) A feature that's in develop may sometimes need to wait for something (QA, business validation, a go-ahead, whatever) to go to master, or
2) A feature that's in develop can ALWAYS go to master at any time.
In the first case, you can have feature X blocking all other features because it's in the same branch as them, which is the problem the GP is describing. In the second case, the two branches are the same, so why not just merge into master directly?
It's always #2, but just because a feature has been approved for master, doesn't mean all the features approved for master are stable together.
A feature might be stable as a standalone, but in virtually every software suite, features interact with each other. That is what develop is for. It's where all the feature branches meet and where any instability created by everything coming together is resolved.
Master, on the other hand, is the product of that successful resolution after all the bug fixes.
I've found that that generally leads to problems, so I prefer to have the feature that is going to be merged last be responsible for fitting in with the rest. That way, as described earlier, I don't have to wait for features that can't be merged now to merge the ones that can.
How do you know which feature will be merged last? In the teams I've worked in previously, everything happened in parallel. You had no way of knowing what feature was going to be merged when. So, essentially, we completed a feature-branch, tested it, and merged it into develop. Then, at set intervals, we did some heavy testing on develop and fixed any outstanding bugs, before creating a release by merging to master.
1) A feature that's in develop may sometimes need to wait for something (QA, business validation, a go-ahead, whatever) to go to master, or 2) A feature that's in develop can ALWAYS go to master at any time.
In the first case, you can have feature X blocking all other features because it's in the same branch as them, which is the problem the GP is describing. In the second case, the two branches are the same, so why not just merge into master directly?