How can I access pages served by hosts behind VPN through web server that acts as a gateway (thus as a client not connecting to the VPN)

So the configuration is as follows: I have an internet accessible Web Server that also hosts a tinc VPN. Let's call it the gateway. Connected to that VPN are other Web Servers which are not accessible via internet. Let's call those VPN'ed hosts.

From the gateway, I want to serve a page that provides access to the pages of the VPN'ed hosts. Now, I understand this sounds like a proxy, however, I am unable to think how to set it up as I don't understand what link would a client click on to get those pages.

My idea would be to make a link a POST request and have node.js (or whatever suits this best) to do some kind of ajax request through the VPN network and serve the page. The problem I see with this is that the pages are not simple static HTML. They have webhooks, upload, settings that need to be forwarded through the gateway somehow. Is this the way to go, or is there a simpler way I am missing?

Obviously one solution would be to connect a my client to the tinc VPN and have direct access to the VPN network but that is not an option for me.