I don't know of anybody that has ever been granted a waiver for the age 23 rule. Back in the day there were several people that worked for ACA and had the time and experience to upgrade well before their birthdays... one was hired on at the company with almost 1500 hours, including some turbine when he was 19 years old... he still had to wait till his birthday to take his oral (when he finally did upgrade he jumped so far up the CA list he didn't sit a day of reserve).
There's a reason for the age limit, and now that I am a bit older it makes sense to me. Don't be in too much of a rush to upgrade- get into the airlines and get on the line... I think you will find that 2 years is a good time frame to get a grasp of what is going on, and the expecations/regulations that you will have to meet.
Just be sure that as the FO, you are observing what is going on and playing a proactive role in your learning. If you aren't asking questions about how decisions are made or observing what your CA's do, then you aren't doing your job. Take the time to learn what they do, by duplicating their work (read the releases and come to your own conclusions about the weather and the flight, then compare your decisions to what actually happens), and paying attention to their duties (like filling out the flight log and writing up MX). By doing that, when the time comes, you will breeze through your upgrade.