Board management vs custom fields

[alorenz]

I can't find a straightforward solution for the following scenario (which should be pretty common) -- am I missing something?

* I'm coordinating a small team in Trello: I maintain the data for 100-200 small tasks -- locations, appointments, what needs to be done etc

* About 70% of those tasks I do on my own, 30% with various team members

* Team members should be able to see only the "team jobs" (i.e. those latter 30%, ideally only those that they are personally assigned to)

* They only need to see the data, not change or edit anything

* Each task has an estimated completion time (hours per person)

I currently have a "main" Trello board for 100% of the tasks, and a separate "team board" where I copy over the "team job" cards via Butler. Not ideal since it creates redundant data, but OK-ish as nobody (except me) can mess up data even by accident .. the team isn't all Trello power users and I don't expect them to be.

--

Now I would like to upgrade to Premium to achieve two things:

* Get rid of all the duplicate data and use mirror cards (or something to that effect) instead

* Implement a simple overview of total time estimated, in all cards, ideally sortable/viewable by list or by month or something.

I thought this would be easy -- simply throw in a few custom fields and sum them up -- but right now it looks like a catch-22:

* either I use mirrored cards, then I cannot access the custom fields in the mirrors

* or I sum up time in the original cards only -- but then I need to live with my clunky Butler copies forever.

For the time overview, I've looked at the Sums, Costello and SumUp power-ups (Sums looks like the best solution right now), so that part is covered. But I don't want to maintain umpteen copies of the same cards forever .. particularly since I've already managed to edit copies instead of originals more than once, and right now I have only *one* team bord which may change in the future.

So, what is the Trello way to do this? How can I provide read-only access to a *subset* of cards, while still being able to access custom fields in all cards myself?

I don't care whether that subset is defined by list, board, label, member or anything else. But I need to reliably restrict access to everything else -- giving the entire team access to all data is not an option.