Modify default Contributor and Member access levels

Hi Team,

We want access levels as follows:

Admin - Default

Member- Default

Contributor- Can view all the contect of workspace and can download reports and data set, however should not be able to modify, overwrite any of the existing report or dataset in work space.

He should be only able to view and "Download report data set for any customization" and can upload it to his personal workspace only. 

Viewer: default

it is at workspace level, so that power user in the org can use dataset for customization or new report build. "Apart for Analyze in Excel"

Regards,

Manveer Nakoti