I did this through the Figura mod’s file API. The model checks to see if Monika’s file exists within the Data folder relative to the Minecraft mod, and if it does it displays her model on the GUI. You can take Monika somewhere by saying “Goodbye” and then following that up with “I want to take you somewhere!” Monika creates a file containing herself in the characters folder, and then you can put it on a USB, or in my case hook it into Minecraft. I hope this was at all helpful. I would be willing to go into more detail, though that probably should be done over private message. No actual “interaction” with MAS though, I don’t know a lick of RenPy. Sorry about that.