I recommend creating a testbed vault for prototyping, then control your boss's group visibility based on workflow state. That will be the most conservative approach which will avoid controlling permissions by individual. I usually try to stick with this approach unless it is unavoidable.
2nd option: In your testbed prototype vault, populate a hidden datacard field with a variable named "leadership-visible" and a default value of "no", then use that field to change the value to "yes" or "no" based on location in the workflow, then modify the saved search to show only files with a value of "yes". I've had to do this before and it works well for limited visibility. You may need to make minor modifications after you get it configured so it gets more "polished" with time based on need. This is a silly approach but works ok. The leadership users could still navigate into the system to see more so use this approach as a last resort.
I recommend avoiding moving files to a different vault on archive. Version history will be lost and it creates an extra place to go find files. My recommendation is to create an archived project state, disable viewing permissions, and enable "ignore permissions in previous states" flag on the archived state.
See this thread https://forum.solidworks.com/message/357298#357298 and how I configured it. It works well.
My boss would not be okay with limiting his viewing rights. We do use permissions as you have listed for other departments (production and engineers). In fact, we use very similar procedures as you have listed in your example thread for our obsolete and impounded files.
Since the files will lose their history, I will defiantly avoid the parallel vault route. The solution that has been suggested here is to move old files out of the vault. I really want to avoid this as we would lose so much valuable data.
I need more clarification on a solution that would fit what your boss needs. Could you clarify what you are proposing as a solution? It sounds like an individual custom solution to control what he sees. Like maybe a dashboard?? See my webpage. The main page has one. Simple Excel report with a graphical interface. There is also Razorleaf's solution EPDM Dashboard built into Outlook http://razorleaf.com/2013/03/epdm-dashboard/
There are some members here who have provided custom programming solutions to recreate history but that is going to be big.