Relative Rank with Varying Dimensionality - Fact or MDX?

I have a need to show the relative rank of peers across varying dimensionality where the siblings are not displayed on the screen. For example, after viewing revenue for Dec09 for their site, an end-user's analytic progression might be to switch to rank analysis:
• Site1 ranks #3 out of 6 for Dec09
• Site1 ranks #4 out of 6 for Dec09 in a ProductA (anchor on Dec09, cross-drill to Product)
• Site1 ranks #1 of 6 in Dec09 for GLAccount123 (anchor on Dec09, cross-drill to GL Account), etc

Users are likely to have security set on their Site meaning they can see their data but can't see their peers. I want to be able to show them their relative rank but not show them their peer/sibling data. Make sense? It seems they would have to be facts in the fact table rather than MDX formulas. Thoughts?

(Also, I welcome any re-posts, I did some searches but didn't see anything related)

Thanks,
SMC