Mansard roof window cladding problems

I am currently in a battle with our contractors and I need to ask you guys your opinions.

Recently we hired a roofing company and a window company to do renovations to the exterior of our home, I coordinated the two contractors in effort to have the job done properly, I understood the complexities of the style of home/roof and realized I needed to have them work together in effort to achieve a seamless installation of our new windows. This did not happen, instead of following my instructions they did it completely wrong! the roofers installed step flashing around all the windows and because the flashing is woven in with every shingle the window installers were not able to do a return or tab out under the shingles, this has resulted in them having no choice but to literally "glue" or attach the cladding to the shingles with calking! when I complained about this the roofer said "this is how it's done!" he said that the cladding needed to be over top of their product and that there was no other way to do it! My issues are that this installation will fail, the cladding or metal work will eventually be forced off by ice, wind and heat exposure, in probably as little as 3 years. I have been told this by other contractors as well. what do you guys think? should I have them tear it all down and start again? I suggested this and they flat out refused! what do I do next? threaten law suits? well I did that as well and they said go right ahead! is this a court case I would win or am I in fact stuck with what I got?