So I've been working with Ved for a while now, and I've got to say, it's pretty much changed the way I've made VVVVVV levels. But something that would be nice is a little button that reloads the assets of VVVVVV. That way, if you're working with a level that has custom tiles, you can easily reload the assets of VVVVVV without having to reload the level. Just a thought.
Also, something else that would be nice is some other basic drawing functions for walls and backgrounds, etc. For example, a rectangle tool, paint bucket tool, etc. We've already got undo/redo and cut/copy/paste, which is nice, but there are some times where I do wish there were more editing features. You can see these features present in RPG Maker:

Though to be honest, I'll probably live without this feature. I'll let you decide whether or not you add this or not.