Global prioritization of all Master Features

As part of our strategic planning process, we want to prioritize all Master Features (irrespective of product line/product) in our entire portfolio.  Right now, there's no way drive prioritization at this level. 

We need to stack rank and prioritize each Master Feature against each other, and we only want a handful of users to be able to modify/update the Global Priority (stack ranking) of said Master Features.  We also want to restrict the ability to change the Global Priority of a Master Feature to a small number of users (and do not want each Product Owner to be able to edit this value).

Using an Aha! Scorecard is not ideal, because each product can have its own scorecard and thus scoring, can be updated by anyone with those access permissions, and doesn't require unique values. 

Right now, we have generated a List report which gets us part of the way there, but will have to pull this into Excel to re-prioritize each time we groom the backlog (2 weeks).