Currently Import is either on for all tables or off for all tables for a security role. There are many reasons why you would not want to have end users importing data into tables that they have permissions to create/read/write/delete - chiefly to keep the end users from creating problems with inappropriate data (i.e account where there are many that have the same name but may be in different states or countries or have different account numbers and the end user isn't skilled at altering their import to utilize different lookups, etc.). Our only recourse today is to turn off import for all but administrators however there are some tables that would be ok for the end user to import to (i.e. contact, lead) but without the granularity in the security we can't.