Proxying an iframe via nginx to edit it via JS?

Question

Nginx

Hello! An interesting question:
You can edit iframe elements if only CORS allows, an external site. Is it possible to proxy an external site through nginx and set up a policy through nginx in such a way that it is possible to edit the iframe, but there would be the content of the external site.

Something like this:
my site -> iframe -> proxy <-> example.com

Or will there be problems with the iframe in this case?

PS I want to translate the contents of the iframe into another language, there is some information there.