You`re in the perfect position to gradually reduce your nicotine intake to zero then quit vaping too, especially with the COPD.
Well that`s the responsible advice, I have a friend who also has COPD, like you she vapes the 88 Vape menthol but unlike you she still uses the Ego type beginners kit. On occasion I have mixed her some 30/70 menthol and reduced the nic down to 3mg without telling her (she only takes tiny drags). Although she found it smoother, she said it wasn`t as satisfying as the ready made, so if your coil can handle the thicker juice, bearing in mind your longer drags, I would say try it and see how you get on.