Approach

I did a research. And even asked the community for any existing examples:

P.S. I was looking for any solutions besides iFrame.

I have successfully built Polymer with AngularJS as a nested component. But, somewhere on forums, there was a restriction about doing that. So I decided to go lower level and built the same approach on the level of Web Components.

Web Components solution

Solution relies deeply on the single feature from Web Components standard. HTML Imports: a way to include and reuse HTML documents via other HTML documents (spec, tutorial).

Idea is to predefine components as HTML imports, while each of them could include their own scripts and styles. So we can decide on the top level which HTML import should be presented in DOM at the moment, and rest of things should be handled by the imported document itself.

HTML imports driven microservices

Shell — is a top level wrapper which consists of component picker and container for components. Also should include views or controllers which allow user manipulating components.

Container — the actual root place where HTML of nested application should be injected. (It should have a single entry point for all nested apps).

Component picker —service which allows managing nested application which is active at the moment.

HTML imports — our abstract microservices. Could be whole apps written in different frameworks.