Hi Nitesh,
From what you describe, this would be a good case to use variables in your analysis authorisations. You can specify a variable value for the BUKRS field and have a couple of options to populate the values which are picked up in the query execution.
You will need to ensure that you activate the istep to read customer exit variables and have the query variable set as customer-exit. Once those are complete, you can create a custom table to maintain the mapping of groups to company codes, or to read the company codes directly from your ERP system (if you want to base authorisations on what the users can see in ERP) and populate the table with those values.
However you populate the value to the variable, I think this approach will get you closer to minimal maintenance going forward. Enhancement RSR00001 should be implemented, some help documentation for this below
http://help.sap.com/saphelp_nw70/helpdata/en/1d/ca10d858c2e949ba4a152c44f8128a/content.htm
Hope this helps,
Tom