I am thinking about making a plugin that would allow users to add banners within their application. The ideal way that I can think about doing this would be to allow the administrator to choose what is shown in conjunction with these banners by allowing them to choose what plugin would be pulled in.
Essentially, this plugin would operate as a frame around another plugin. Is it currently possible to load another plugin into a "frame plugin" like this, or is that no doable?
Unfortunately not. While Plugins are autonomous they communicate with the core apps' API's.
However, if you to use something like a Folder Plugin you can use the carousel to add your banners and make them clickable via an action item (already built in) ref:
The banner would be there every time the user when back to the home screen