If you are not too worried about earlier decline in cognitive abilities then it is something which could, in theory, give you some well deserved peace.
But, I have read some studies that benzos actually worsen PTSD in the long run. There are some conflicting evidences, as some sources state that anxiolytic effects are preserved even after chronic use. My subjective feeling, as I am on benzodiazepines for almost 2 decades now, is that they do not retain added therapeutic effect but they keep you out of the withdrawal which is seen as anxiolysis. Coupled with amnestic effects I can see why it would be beneficial for PTSD. I can certainly see why withdrawal would put you into quite unease to say the least.
Minuses are - cognitive decline with higher possibility for dementia, psychosomatic illness, higher risks for falls with fractures and all that jazz. There are reasons why can be beneficial to stop benzo use, but there are certainly cases when that would do more bad than good. My reading from your posts is that you don't need extra pressure and that stopping benzodiazepines would maybe bring more harm than good for you.
I must say that it is your life and you know what you can handle. It is your decision and I am giving my opinion which can be wrong when applied to your circumstance. But you have asked so...
Regarding opioids, I do not see them as great threat for ones health when they are taken responsible as you are doing. One thing that would worry me would be if one was to go from oxycodone to methadone. That could be a recipe for disaster. I know that you were/are thinking to try methadone as oxycodone dosage does not serve you well. In that case I would pay a lot off attention on how my mind/body is reacting. For me, methadone was the best painkiller but at the same time it made me flat. I did not like how it was influencing my personality at all. But maybe that is just me.
To conclude, benzo/opioid combo is not healthiest combo I know. Benzo part is more problematic in my experience and knowledge. But, you are not some average person who worked desktop job and retired without ever comming to contact with dark and malicious part of this Great Act we call life. From what I read you need as much peace as you can get, not "as much sobriety you can get". If you think that this combo is making your life bearable then use it.
I know people who went to war and now suffer PTSD. Most of them use antipsychotic/benzodiazepine/mood stabilizer (anty seizure med) mix to help them cope. I think that benzodiazepine/opioid combo beats that triplet every day.
I am sorry you have encountered evil that resides in all of us and I hope you find strength to accept it as the part of life.
I wish you find your peace and I don't think benzo/opioid combo is something to be avoided at all costs.
Peace,
Soma