With the Experimental Physics and Industrial Control System (EPICS) toolkit being used around the world, modifications to the core software must be very carefully designed to avoid breaking existing applications; this often limits the changes and new functionality that can be introduced. A new way to extend the EPICS input-output controller (IOC) was discovered recently that should be fully compatible with most channel access (CA) client programs; if the IOC supports optional postfix modifiers to the process variable (PV) field names it publishes, it becomes possible to add several features to the EPICS toolkit. However if those field modifiers can be written in standard JavaScript Object Notation (JSON) syntax they can encode a complex data structure and become very powerful, permitting client-specific configuration of individual CA channels without necessitating any changes to the network protocol. This paper will describe how EPICS Base is adding support for JSON encoding and field modifiers, and will discuss other features such as record aliases that have been introduced to help control systems evolve.