That is what maintenance drugs do best like subs and methadone! They help keep your cravings away for other opioids, and keep you well. Methadone actually gets some people pretty faded as its a relatively strong full agonist opioid and its very long lasting as well, but that isn't really the point of these drugs to get fucked up on them, they are for people that want to change their lives for the better. Methadone clinics can be a pain in the ass though I have heard, and you have to go in everyday, usally early in the morning to have them feed u your daily dose, and once you gain trust they give you some to take home with you for a few days, and the longer you stick with it and do well I believe they increase that to weekly take homes, from what I have heard. I have been on subs myself, and I love them now, but when I first got on them it was a bit hard not to want to do oxy/dope, for like the first week or so I just wanted to do opiates instead but I forced myself to stick with the subs and in 1 to 2 weeks I was fully adjusted to subs and had no more cravings for dope. It is different with everyone, but if you have just been doing kratom lately, I would suggest subs as they are much easier to get. Usually a sub doctor will write you a script for like 8mg a day or more to start for anywhere from 2 weeks to a month supply at first then it starts becoming monthly every visit but at first it might be every 2-3 weeks you have to go in, just so they can be sure your doing what your supposed to be and not screwing around and just continuing to use opiates. I have been on subutex for years and its become one of my favorite things to take surprisingly, I enjoy the nice buzz I still get from them along with my benzos.
But in my honest opinion in short, I would try subs first since its less of a hassle everyday, if that doesn't work switch to methadone. Also if you just want them to quickly get off opiates, you can also choose to do a quick taper with subs and be clean within like a month from all opiates, I couldn't do it because I just kept relapsing like that, so I went on sub maintenance and have been on it off and on for like 5 years now with a couple relapses in between.