Do you mean you want to inject the accordion into some HTML markup that isn't created by ExtJS?
That should be easy enough.
Get rid of the viewport. Add in a renderTo on the accordion:
That works for me. It's similar to what you had before but, importantly, I've completely got rid of the viewport.
I'm still not convinced I'm actually answering your real question but I'm afraid I'm struggling to understand what it is you want.