In short: this tool is great as wedge, not so as KERNAL patch. A program that uses this tool needs to be fully aware of it anyway. In principle, it gains its merits just like any of the known BASIC extensions - you invest some memory into the wedge to simplify some other aspects in your own code.
As you pointed out, you really are talking of a few programs that would benefit from this, so it really doesn't matter what you break. Luckily BASIC programs will relocate automatically, so that doesn't matter. I think the main benefit of such a program would be simply to have a larger screen to make listing/editing nicer. So, with a kernal switcher you would select this, do your editing etc, save and switch back to normal kernal. If it became a "standard" then perhaps people would develop some specialized software for it. Hard to say. In any case, it's an interesting concept.