While there's nothing stopping you from doing so I would be wary about it. Even though the service will be internal you might still need to use third-party soft

While there's nothing stopping you from doing so I would be wary about it. Even though the service will be internal you might still need to use third-party software/tools in the future that will be incompatible because of this. For example, will you need to use a 3rd party request library? Will you need to set up some sort of proxy (NGINX, HAProxy, etc.)? Will you need to use a cloud load balancer (I'm not sure if they would send a request payload for GET requests)? For open-source solutions you might be able to fork them to add this behavior but why do so to begin with? Is there a specific reason why you don't want to use query parameters?