good to see you to post about this issue. I don't know much about diaper fetishism but I'll add some my thoughts about my coping mechanism.
Firstly I'm glad that you decided to share such intimate things with us.
Please try to discuss it more, I hope someone with more experience could add to this discussion.
Please try to look why do you want to deal in destructive way to your body when you are speaking about "permanently disable my ability to hold it"? What are main feelings in background that force you to escape from reality into excitement of such ideas?
Are those some negative feelings like loneliness, fear or something similar? Are you have such thought after some happenings or talks?
Can you try to think more about it?
When you wrote about that way of "self injuring" I must add that I recognized some my patterns related to watching porn (when I also in some twisted way hurting my self). I went from some regular stuff to some very kinky.
In my case I don't think that is at all important what are exact details that are giving me highs. The more important is that I can't stand feelings of loneliness or when something bad is happening and I don't have any control over it, like some natural disaster.
In my therapy we are discovering slowly those negative feelings and believe me some of them are not at all connected to my experience as molested boy. Main drive are very negative feelings of isolation that I've experienced back in my childhood when I couldn't talk about some important issue (including touching by other boys) with my parents and particularity with my mum. When I see that some important people are not seeing my needs and don't give me any support in some moment when I need it and ask for it I'm desperate and very hurt. You can guess that I'll be browsing porn pages couple hours later if those feelings would stay with me, it just becomes overwhelming so I need to escape reality.
Sorry I don't want to hijack your post but I just wanted to share my experience about dealing with self destructive thoughts and actions.
I'm proud on you that you decided to talk about it here, you were very brave
Keep sharing with us!