If a user has a list of Companies (that may already be in CRM) from an external source it should be possible to import these Companies as members to an existing marketing list. Same goes for contact and lead members on marketing lists.

I saw another similar feedback item in this forum which was rejected by the product team because MS is focusing on Dynamics Marketing. That is a really weak arguement. First of all tons of CRM customers will NOT be implementing Dynamics Marketing due to it's high price and/or complex functionality. Secondly the Marketing List functionality is at the core of the CRM product. It is used in many scenarios that is not necessarily "marketing" related. So to stop focusing on this feature because of Dynamics Marketing is not acceptable to most customers and partners.