Seems like buying a Ferrari and putting a pinto engine in it. Sure it's still a car that runs and will get you places, but why'd you buy the Ferrari?
A brewjacket "works". I use air quotes, because there is not a measure of how good it works. It's also going to defeat any pressurization capability completely. It will also kill any bonus of being air tight. It'll basically kill any advantage at all that a stainless conical brings to the table.