I was on methadone for 4 years back around 2007. It literally saved my life. I was grateful for it. I realized though that it wasn't the answer for recovery from addiction but I was able to live a more normal life. I think there are a few different opinions on this. But you and I both know how hard it is to come off opiates.
You sound like you want to wean off them eventually and It sounds like you are motivated to get well and be in recovery.
Don't do anything without a doctor's guidance. A sponsor is someone to guide you through the steps. If that is a problem for them because you are on methadone, find a new sponsor.
Being on methadone is a heck of a lot better than running the streets looking for heroin and shooting up. I have been off methadone for almost 4 years and I am glad it was there when I needed it.
I was not doing meetings at the time and had no sponsor. I was not attempting any real recovery at the time, I just wanted to feel better from the dope sickness and I did and was able to function like a normal person.. Sounds like you have a plan and do want to wean eventually and work a program.