@JSWolf - it is *YOUR* solution which while it might make you happy is not necessarily *THE* appropriate decision to be made for every other user out there. As you well know calibre has in excess of 6 million users. If enough users felt that strongly about it Kovid would have changed calibre's conversion behaviour - there are reasons for why it does what it does which are just as important to other users. Personally I find large covers a complete and utter waste of time and disk space. All this drama for something that users immediately skip past on their way to reading the book (Kindle users don't even have to skip it?).
Without this option in Modify ePub if you want a bigger cover you can change your output profile and just run the plugin again. There is no end of the world doomsday scenario here, the plugin can be re-run perfectly safely for those who now want bigger covers.
As I said above I will consider an option to not resize for a future release, but it isn't important enough that I am going to sacrifice a rare sunny evening in london for. And if your world will end without it, feel free to go back to using Tweak ePub to substitute your covers like you used to do. I'll get over it, honest.