Dev blog: Introducing the Mining Ledger - New tools for miners in EVE Online

Siphons are perhaps a “missed opportunity,” someone posted an F&I wondering if they could be changed to steal fuel, but it wasn’t too popular.

You are right about no compensation for certain obsoleted items, and for the reasons you state. But POS gear specifically has been mentioned in past dev blogs.

…disabling of Starbase Moon Mining Arrays and Starbase Reactors when Refineries are released, as well as eventually removing the types associated with obsolete Starbase functions completely and distributing appropriate compensation to their owners.