You are so well-spoken - obviously, you know what you're doing, but Tink sure doesn't!!
You're way too smart for me to offer any advice, but I would say that the diapers are the way to go - for now at least. We had a rescue yorkie that had some serious issues and submissive peeing was only one of them. I went the diaper route just to save some of the stress in the household. We all needed the break from the stress (and cleaning). Maybe after the holidays, you can regroup. But for now, I'd just say you all need a break. And who knows? Maybe it'll be the magic ticket if she doesn't like to be wet.