From my understanding and overlay was in the works to be added to the Runemate API but is not of top priority. One could look at the development tools, of which i believe, one of two, are open-source.
I would recommend posting your suggestions on that bot's discussion thread and see if the bot developer will be willing to add support for the functionalities you want.
To add to what makutu said, also execute the RM client using the debug button in your IDE. I presume you use intellij? When you rebuild, it should tell you it hotswapped some classes.
I see there is a directory where the path data are stored, would i be able to replace said paths with my own? Parametric's tool will be used to generate the paths, i believe he posted it in slack a while back. Would this be possible? @Cloud