Giving report user the ability to group column data for future use

Hello All,

I have a requirement where the user of the report should be able to create groups with the data in "Accounts" column, so that they or anyone else can use it in future.

I was thinking of creating a landing page before the report parameters are displayed and then giving the user multi-select option for Accounts column.

Once the user selects the accounts and names the selection, it gets stored in a seperate table in the data model.

and hence, when the user goes to report, I can give them drop down that points to this seperate table to give user a selection of account groups.

The Problem with this approach -

1) This grouping is not report specific and should be used in all the reports - I dont know how to make this table updatable and accessable across different reports

2) there are 1000+ users and 200+ accounts and 100+ reports. I am anticipating about a thousand groupings to be made by different users for different reports.

Thank you for your help!

-AK