The only thing I would ask is make the hundreds of old custom scenarios compatible with the new version down the road. This appears to be possible once the editor is released. BTW, a supposedly more powerful editor.
Beyond that, and a few UI tweaks, I don't think the new version is so bad! I will definitely be buying at least one DLC once the editor is released as a patch.
Actually, many people, including me, have run into many situations where movement and combat do not work properly, including units that just disappear, and many other problems that are listed in detail in a couple of threads on the Slitherine forum. These leave the new version broken, in my opinion. I am certain that Slitherine will try to fix it, and they should be able to, but supporting the old game until the problems are fixed is the best alternative.