Subscription Contracts - is there a way to set these up and ship items that are not IB trackable

Our situation is that we have recipients wearing or implanted with medical eqipment and we need to have good records of who has what items. 

We also ship quarterly magazines to recipients and many subscribe annually to receive batteries and small consumable items on a quarterly basis.  Subscription contracts seems to be an ideal way to do this but we do not want to have our recipients Install Base cluttered with all the magazines and batteries we have shipped to them.

Subscription contracts seem to be set up so that only Install Base trackable items can be defined for shipment.  Is there any way of removing this limitation?