Unable to set up Service Item purchased and purchasable

At a client location there is a need to set up Service Item purchased and purchasable as the service item should be purchased and then sold trough Service Contract module. Currently when I am trying to tick and save Purchased and Purchasable attributes for such item I got an error:  APP-INV-05702: Purchased item must be disabled for non subscription contract item types. So this functionality now is not available and there is a related ER: 'ER  Bug 10017120   : HOW CAN I ATTACH REPOSITORY CONTRACT TO A PURCHASE ORDER & HOW DO I SEE THE CONT. The question: does anybody have experience in customizing this functionality (to make possible to setup service item as purchased and purchasable) and have impact analysis information? What is the functionality dependency?