Context-sensitive lists for Primary Contact on Opportunity

Hi,

For service requests, tasks etc we can see that when an account is specified, the contact lookup displayed the 'Contacts for Related Account' list. 
For Opportunities we do not have this, as we don't have a lookup option for Primary Contact in the Edit screen of the opportunity. The contact always has to be added via the related information section. 

How can we provide our users with the 'Context sensitive list' option for primary contact on opportunities? An enhancement request for this has been declined, are there alternative solutions to make the process of adding a contact to an opportunity easier for the user?