As someone that has worked on a similar project before -- I should caution you that allowing POST requests and such can open up a lot more potential for abuse (comment spammers, web-mail spam, etc) so you should add some rate limiting per-visitor-IP/target-domain or something similar before implementing this.
right.. thanks for the heads up ! But since it's a self-hosted solution, it would be very easy to just circumvent the rate-limiting and use it for malicious purpose ?
Right, if your goal is privately hosted/accessible instances then it shouldn't be a problem. Just mentioning in case the goal is to offer it as a public service as it is at your main domain.