I think you can create a new file $:/plugins/Gk0Wk/echarts/addons/TheBrain4Stream.js or something, and add getStreamLinks and getStreamBacklinks in that file instead?
So you don’t need to change the wiki.js in the echarts plugin.
And you can use Gatha Gatha Plugin: Beta Release - Create and Distribute Tiddlywiki Plugins - #94 by linonetwo to pack it as a plugin.