How to rollup multiple directories seperately with one output

So, I have a directory

mods/
-core/
--index.js
--scripts/
---lots of stuff imported by core/index

This works with typical rollup fashion if you want to export to for example mods/core/index.min.js

But I have many of these mods/**/ directories and I want to take advantage of the fact that they are rollup'd into iifes. Each mods/**/index.js will, rather than export, assign to a global variable that we presume is provided:

core/index.js

import ui from './scripts/ui/
global.ui = ui

someMod/scripts/moddedClass.js

export default class moddedClass extends global.ui.something { /* some functionality extension */}

someMod/index.js

import moddedClass from './scripts/moddedClass'
global.ui.something = moddedClass;

So hopefully you can see how each mod directory can be rollup'd in typical fashion but, I need to then put the actual iifes inside another one so that:

mods/compiled.js

(function compiled() {
  const global = {};

  (function core() {
    //typical rollup iife
  })();

  (function someMod() {
    //typical rollup iife
  })();

  //a footer like return global or global.init()
})();

Any help towards this end would be greatly appreciated. The simplest possible answer, I think, is how I can simply get a string value for each mod's iife instead of rollup writing it to a file. At that point I could just iterate the /mods/ directory, call rollup on each index, and build the outer iife myself.

via Danie Clawson