Website forwarding whilst changing values

Hello,

Haven't really found somewhere to post this so here it goes:
Any ideas whether it is possible to host a website, which forwards from another whilst changing a certain value?
For example: I have a non-secured (HTTP) website, which has the following data inside (alongside buttons, design, cookies etc.):

located in x.com

Hello, my name is John, how are you?

I want to create a new website (y.com) which takes the data from x.com (alongside design, cookies, WS etc...), and change all John to Edward.

located in y.com

Hello, my name is Edward, how are you?

Similar to a phishing website (which is not the purpose of this), I'd like to know if this is possible without having to download the contents of this website and upload it. (as I want all websockets/cookies and other functionalities of the website to remain)

Constraints:
- I do not have access to x.com's server
- I only have access to x.com's domain name
- Perhaps do that to certain images as well
- Would that work for CSS as well?
- over 100+ simultaneous connections possible
- Consider x.com updates every second

Example:
Let's say we have an HTTP (non-SSL) version of, say, BBC, and would like to change all the words 'British' to 'Lebanese', with the consent of the BBC, how would that be possible?

Possibilities thought of:
- Using some kind of relay application that forwards all data from x.com, whilst editing the body?
- As I have access to the domain, perhaps pass it through my own nameserver and do some kind of the magic CloudFlare does (adding stuff to the body (?))

In other words, making good use out of the Man-In-The-Middle attack / Proxy server.

Thank you in advance!