I believe it would be a useful feature to be able to share segments of code between scripts.
This would save on code redundancy and usage of the limited script storage space.
I guess it would essentially be working as a module system but only internally to script runner. Where the modules or even just specific methods could be imported/called inside Script Listeners, Scheduled Jobs and even the Script Console.
My use case would be storing a helper method I wrote, for handling all REST requests and processing the response. I copy and paste this into all my scripts for convenience at the moment.