I say give brake fluid a go if you are ok with gambling on the small investment. I think I got my half litre for a fiver so it's an affordable experiment.
I feel your pain and I share your quest as I was stripping hundreds of models this past year (and I still am). Some were bastards to strip, some were not stripped to satisfaction. See if I can share my experiences a bit for your benefit.
The thing I found with stripping hundreds of models is that every agent eventually came up short. Sounds discouraging, but need not be so bad if you can employ several agents as long as one will work (sounds like a spy novel this)
More precisely, I use a dettol-type, isopropyl alcohol (isopropanol) and brake fluid. I consider all three to be my work horses and worth buying in the long run. They have all had their triumphs and failures. I think there is merit in having the brake fluid, as there is in having the others, as each has been the most efficient at times. They have also all come up short at times. I suppose that just comes down to there being great variety in paint types, and how the chemistry works out with various stripping agents. On top of that, primers and varnishes may complicate things further and give you different results.
I personally suspect that the kill-all is somewhat of a mixture of wishful thinking and urban myth. There are tons of testimonials saying a product "was awesome, it will strip everything and I never use anything else". Meanwhile, you can find testimonials of people saying "hmm funny, I tried it and it didn't work for me".
I don't think going nuclear is the answer either, as if there is something out there that is an unstoppable beast at stripping miniatures, it may very well also strip your lungs. Believe me, I am not trying to babysit or being up in arms about the environment, just saying there is actually such a thing as gravely hazardous chemicals that have caused people irreparable damage. If you try though, post results. Relevant to your search however, I don't know what substance that would be in any case. I've only heard rumours about airplaine paint strippers so bad it will strip your ancestors.
Seriously though, brake fluid can work. But will it? Never a guarantee, that's what my own experiments told me - but sometimes it came out on top in my toolbox of three.